Chapter 1 - General physical examination

In this chapter, we consider some aspects of the general physical

examination that are especially pertinent to neurologic evaluation. In later

chapters we will cover other aspects of the neurologic examination, the

involvements by specific disease processes, systems abnormalities, and

symptom complexes. Not all elements of examination can (or should) be

conducted on every patient. Indeed, if all the examinations that we will

describe were carried out on all patients, it would be difficult to see more

than several patients a day. An efficient diagnostic approach demands

careful evaluation and utilization of historical data in a problem-oriented

fashion. This demands that the physician focus on those parts of the physical

examination that are pertinent to the specific problem or problems elicited

by history or by a basic screening exam.

Vital Signs

Of particular importance is evaluation of the respiratory rate and pattern in

patients with depressed consciousness. This topic will be elaborated on in

the section on the evaluation of coma in Chapter 24. Bilateral involvement of

the brain stem from the diencephalon through the medulla may be

associated with characteristic and therefore localizing patterns of

respiration at each level of involvement. Unilateral dysfunction is usually not

reflected by respiratory abnormalities. The abnormal patterns of breathing

most likely represent loss of higher control of the primary medullary

respiratory center. Suppression of medullary function by metabolic or direct

mechanical involvement results in hypoventilation and, ultimately, apnea.

Figure 1-1 is a schematic of respiratory patterns associated with

bilateral lesions at various levels in the brain stem.

Blood pressure is frequently elevated considerably above pre-morbid

levels when there is increased intracranial pressure and then drops when

intracranial pressure is lowered (although this usually is not of much

localizing value). Blood pressure is also frequently elevated during an

ischemic stroke, possibly a compensatory response to loss of part of the

cerebral blood supply. Typically, the blood pressure will revert to baseline

level over hours to days without need of therapeutic intervention. Attempts

to lower the pressure, unless at extreme levels, can be counterproductive

(resulting in further ischemia). Blood pressure drops to very low levels

following loss of medullary function or severe cervical spinal cord damage;

however, for therapeutic purposes, severely depressed blood pressure

should be assumed to be due to non-neural causes (such as cardiac

abnormality or blood loss) until proved otherwise.

Peripheral nervous system dysfunction (i.e., peripheral neuropathy) can

produce symptomatic hypotension when the patient assumes the erect

position (orthostatic hypotension). This can be related to involvement of the

peripheral autonomic nervous system with loss of peripheral vasomotor tone

and can be caused by many conditions that produce generalized peripheral

neuropathy, such as diabetes, alcoholism, or malnutrition (see chapter 12).

Orthostatic hypotension can be detected by recording blood pressure and

pulse in the recumbent and upright position, looking for a drop of at least 20

mm Hg of systolic pressure, or a diastolic blood pressure decrease of at least

10 mm Hg within three minutes of standing. Symptoms of light-headedness

or faintness would indicate that this was symptomatic orthostasis. If the

pulse rate increases as the blood pressure drops, hypovolemia would be

more likely than autonomic failure to be causing the orthostasis. Exercise

prior to testing (which causes a reactive peripheral vasodilation, lowering

peripheral resistance, may exaggerate any orthostasis). Isolated central or

peripheral autonomic failure secondary to medications and metabolic or

degenerative disease (including Parkinson disease) can also be a cause of

orthostatic hypotension or other autonomic dysfunction (decrease in urinary

bladder tone, erectile dysfunction, etc).

The pulse rate may be slowed (bradycardia) or accelerated (tachycardia)

with increased intracranial pressure, and therefore any change must be

considered in a person with central nervous system involvement.

Arrhythmias, particularly sinus arrhythmias, and nonspecific ST-T wave

changes are frequently seen on electrocardiograms of persons who have had

subarachnoid hemorrhage or either hemorrhagic or ischemic strokes. If

atrial fibrillation is present, systemic embolization of thrombus formed in the

non-pulsatile left atrium should be considered the most likely cause of a

stroke.

Head

Changes in the shape and size of the cranium may reflect changes in the

intracranial contents.

In children younger than the age of closure of skull sutures, increased

intracranial pressure is reflected in widened suture lines that may be

palpable and quite visible in radiographs. If the pressure is prolonged, a

mottled decalcification or beaten silver appearance of the skull and

demineralization of the dorsum sellae may appear on x-rays. Bulging of the

anterior fontanelle in the erect or seated infant is a reliable sign of increased

intracranial pressure or contents. Progressively enlarging ventricles,

hydrocephalus, causes enlargement of the skull, which can be observed

easily. Early diagnosis of hydrocephalus is possible by measuring the cranial

circumference during well-baby check-ups (comparing it with standard

charts). Subdural fluid effusions, usually associated with meningitis and

subdural or epidural hematomas, also cause excessive skull enlargement in

infants and toddlers who have nonfused suture lines. Premature closure of

sutures causes characteristic distortions that should be recognized early

because associated restriction of brain expansion may result in neuronal

damage and mental retardation (Fig. 1-2).

In adults, the shape and size of the cranium are less often revealing. The

presence of asymmetric bony prominences contralateral to sensory motor

deficits or in a person with focal seizures suggests an underlying

meningioma, a benign tumor that occasionally causes secondary osteoblastic

activity in proximate parts of the skull.

In both adults and children who have a history of head trauma or in

persons who are stuporous or comatose for unknown reason, the skull

should be gingerly palpated for soft-tissue swelling, which suggests head

trauma and possibly underlying fracture. Ecchymoses at the base of the

occiput (Battle sign) or around the eyes but contained by the orbit (Raccoon

eyes) suggest basal skull fractures.

When the head is gingerly rotated from side to side, the brain, which is

essentially floating in the subarachnoid cerebrospinal fluid and is tethered to

the dura and contiguous skull by cranial nerves, blood vessels, and

arachnoid membranes, is relatively resistant to the movement. The

movement stretches the cranial nerves, the larger blood vessels and the

dura. Under normal circumstances, no significant discomfort is caused by

this stress. However, when the surface blood vessels or dura, which are

sensitive to pain, are already distorted by a mass lesion or swollen with

inflammatory edema as with migraine or arteritis, pain may be increased or

experienced for the first time on shearing. The patient frequently can point

to the area of involvement.

Although not part of the routine exam, auscultation of the cranium (with

the bell of the stethoscope) over the mastoid region, temporal region,

forehead, closed eyes, or (in bald individuals) more extensively may reveal a

vascular bruit arising from an arteriovenous malformation over the brain

surface. The bruit is caused by the increased, turbulent flow in the

arteriovenous short-circuit that makes up the malformation.

In whom should auscultation of the head be considered? The person

with a history suggesting an arteriovenous malformation is one candidate.

This would include patients with headaches that are always on one side of

the head (most patients with migraine, for example, have at least occasional

headaches on the other side) or patients with focal seizures. Of course, in

both these cases, cranial imaging is important. On occasion the person with

arteriovenous malformation hears a bruit, particularly at night when

distractions are at a minimum. Careful auscultation of the head may help to

localize that.

The small child or infant with a congenital arteriovenous malformation

in the area of the internal cerebral veins and the vein of Galen has a bruit

that is audible over the whole head. S/he may have congestive heart failure

from the high flow demands of the shunt, and also an enlarging head, the

result of a communicating hydrocephalus. This is caused by the

arterialization of pressure in the sagittal sinus, which increases resistance to

absorption of cerebrospinal fluid through the arachnoid granulations.

Compression of the aqueduct of Sylvius by the swollen vein of Galen may

also be the cause of the hydrocephalus.

The infant with meningitis and diffuse cerebral vasodilatation and the

infant or child with severe anemia may have diffuse cranial bruits caused by

high flow through the cerebral or diploic vasculature. These bruits are

usually inaudible in the older child or adult whose skull is thicker and thus

dampens the sound unless anemia is severe.

Eyes

There are several features of the eyes that should be considered in the

neurologic exam. The conjunctiva and sclera can show signs of icterus or of

inflammatory, vasculitic processes. A prominent corneal arcus can suggest

dyslipidema which, in turn, suggests the potential for atherosclerosis.

Funduscopic examination can be very revealing. First of all, it may show

whether visual abnormalities are due to refractive problems, including poor

visual correction or opacities (of the lens or cornea). It is also the only place

in the body where blood vessels can be directly visualized. The health of

these blood vessels is a reflection of the health of small blood vessels in the

nervous system (including signs of atherosclerosis or of diabetic vascular

disease that can effect the brain and peripheral nerves).

We will specifically discuss two phenomena or neurologic import,

papilledema and subhyaloid hemorrhage. Papilledema results from

increased intracranial pressure, which occurs when the contents of the

cranium exceed the capacity of the intracranial physiologic mechanisms and

anatomy to accommodate. The major accommodating factors are the

cerebrospinal fluid space (ventricular and subarachnoid) and its ability to be

drained by the venous sinuses, the venous space and its collapsibility, the

ability of sutures to spread in infants and toddlers, the ability of brain tissue

to be compressed and lose substance, the ability of the foramen magnum

(and to a lesser degree other foramina) to transmit pressure to the

extracranial spaces, and finally, the possibility of decreased production of

cerebrospinal fluid from the choroid plexi when intracranial pressure rises

to high levels. The major causes of increased intracranial pressure are

cerebral edema, acute hydrocephalus (blockage of cerebrospinal fluid [CSF]

absorption, relative or absolute), mass lesions (e.g., neoplasm, abscess,

hemorrhage), and venous occlusion (e.g., sagittal or lateral sinus

thrombosis).

Papilledema or edema of the optic disk usually indicates increased

intracranial pressure. When it is fully developed, recognition is not difficult;

swollen, blurred and elevated disk edges, engorged and pulseless veins, and

increased vascularity of the disk margins are the obvious signs. This is

usually bilateral. At these stages, vision is usually unaffected (outside of

possible slight increase in the physiologic blind spot *). With further

development, hemorrhage (both superficial and deep) and exudates appear.

If the process is chronic, filmy white strands of glia proliferate in and around

the disk. It is at this late stage that the patient may complain of episodic

obscured vision. This precedes final occlusion of the retinal arterial supply

and infarction of the retina with permanent blindness. Early recognition is

important in order to diagnose the underlying cause and also in order to

prevent vision loss.

It is usually possible to detect early, subtle signs of intracranial

hypertension. Prior to well-established and easily recognizable papilledema,

the normal pulsations in the veins of the optic disc disappear with elevated

pressures. These pulsations are best seen in the normal fundus where the

veins disappear into the substance of the disk. They reflect the arterial pulse

pressure superimposed on a baseline intraocular pressure; the veins

partially collapse during systole and expand during diastole. If the pulsations

are not spontaneously present (as they are in about 75% of normal

individuals), a minimal amount of pressure on the globe brings them out in

almost all persons who do not have increased intracranial pressure (i.e., less

than 200 mm of CSF). The minimal compression partially collapses the veins

and allows them to expand during diastole. If intracranial pressure is 200

mm of CSF or greater, venous pulsations usually are not present and the

higher the pressure, the less likely there are to be spontaneous pulsations.

**

Papillitis or inflammatory edema of the disk looks very similar to

papilledema. Indeed, in most cases, they are identical. Papillitis is most often

caused by demyelinating processes in young and middle-aged persons (such

as multiple sclerosis) and by optic nerve arterial involvement in older

individuals. It is not associated with increased intracranial pressure. As

opposed to papilledema, however, it is almost always unilateral. The visual

field loss associated with papillitis is usually greatest near the center of

vision, because the macular (cone vision) fibers are primarily affected. This

leads to early loss of color, particularly red, vision. A central scotoma (blind

area) is typically present and thus visual acuity is severely and uncorrectably

limited (see Chap. 3). This is distinct from papilledema which usually only

produces slight enlargement of the blind spot until quite late when the

arterial supply is compromised by compression. Even then, the vision loss of

papilledema is usually distinct because it starts at the periphery, with

central vision preserved until late.

Subhyaloid hemorrhage is a collection of extravasated blood just

beneath the inner limiting membrane of the retina (Fig. 1-3). This is different

from most retinal hemorrhages which occur deep to the nerve fiber layer.***

Subhyaloid hemorrhages are frequently observed close to the disk margins

with an acute, catastrophic rise in intracranial pressure. This is invariably

caused by intracranial arterial hemorrhage (subarachnoid or intracerebral)

or head trauma with hemorrhage and brain contusion or laceration. They

are often seen in "battered infant" syndrome, for example. They appear

almost immediately and frequently on the background of a relatively normal-

appearing retina. They are presumably caused by a rapid and excessive rise

in the central retinal venous pressure, which leads to rupture of the small

venular radicals near the disk. Papilledema may follow within several hours.

On a normal background the hemorrhages are diagnostic and should allow

the physician to avoid lumbar puncture, which, in the presence of cerebral

hemorrhage or cerebral contusion or laceration, could further predispose

the patient to brain herniation (see Chap. 24).

Acute central retinal vein thrombosis, frequently associated with long-

standing diabetes mellitus, can also cause subhyaloid hemorrhages. In these

cases, it is almost always unilateral, however, and may be very large or

distributed in the segmental distribution of one or several central venous

branches. The patient does not appear otherwise ill and complains only of

loss of vision in the involved eye. The visual loss may be surprisingly

minimal.

Ears

In bacterial meningitis, particularly in children, one of the most frequent

portals of entry for bacteria is the chronically or acutely infected middle ear.

The presence of otitis media is readily visible on otoscopic examination as an

opaque, bulging, erythematous tympanic membrane and should be looked

for in all persons who are suspected of having meningitis. Successful care of

the meningitis may depend on eradication of the otitis, which may

necessitate puncturing the eardrum (myringotomy) for drainage in addition

to administering appropriate antibiotics.

The patient who is unconscious and has no history or obvious signs of

etiologic significance should be suspected of having head trauma. In

addition to palpation of the cranium for evidence of fracture and observation

of ecchymosis, the physician should look for a bulging, blue-red tympanic

membrane. If present, it indicates hemorrhage into the middle ear and is

pathognomonic for severe head trauma. Basilar skull fracture with

dissection through the middle ear is considered the cause; however, severe

shearing of the ossicles may be enough to cause tears in blood vessels and

hemorrhage.

The external ear may be implicated in the person with hearing loss,

especially if the deficit is of the conduction type (see Chap. 6).

Neck

The spinal cord, meninges and cervical roots are stretched slightly when the

head is flexed onto the chest. This ordinarily can be done without any

discomfort; however, this is not so when the meningeal sheaths of the roots

are inflamed. Pain and reflex stiffening of the nuchal muscles are elicited

when meningitis is present (called "nuchal rigidity" or meningismus).

Because the spinal cord is pulled by this maneuver and moved upward

slightly in the spinal canal, the lower lumbosacral roots are also stretched

and pain may be experienced in the low back and legs as well as the neck.

Occasionally, spontaneous flexion of the legs and hips occurs on neck flexion

(termed Brudzinski sign). This is a reflex attempt to put some slack in the

stretched lumbosacral roots (with the legs in the flexed position, the femoral

and sciatic nerves and therefore their roots of origin are slackened). It is

usually not symptomatically successful; however, it is a strong indication of

meningitis and other causes of root irritation.

A majority of the population by age 65 to 70 has x-ray evidence of

degenerative disease of the cervical spine. This osteoarthritic change,

frequently referred to as cervical spondylosis, appears to be a product of the

constant trauma of the weight of the oversized human head on the neck

when in the erect position. Despite the appearance of severe cervical

osteoarthritis on x-rays, disabling symptoms do not occur in the majority of

people with cervical spondylosis. Spondylosis does correlate with decreased

mobility (mostly in rotation and lateral bending). Flexion is usually not

terribly limited and there is usually not much (or any) pain reported by the

patient. They also compensate for the loss of mobility, which occurs slowly.

The most important symptoms and signs that can be caused by

spondylosis result from irritation or destruction of the cervical roots and/or

the spinal cord by the hypertrophic degenerative disks and joints. Nerve

root involvement gives localized signs that are positive (e.g., pain and

paresthesias) or negative (e.g., loss of sensation, reflexes and power) in

character. Damage to the spinal cord by spondylosis can result in motor and

sensory symptoms below the lesion due to interruption of the long tracts of

the spinal cord by impingement.

Lhermitte's symptom (or Lhermitte's sign) includes a sensation of

"electric shocks" radiating from the posterior nuchal region into the arms,

trunk, and legs separately or in combination by forcibly extending or flexing

the neck. This signals cervical spinal cord involvement and is probably

caused by rapid distortion of the cervical cord and associated depolarization

in irritated sensory nerve fibers. During extension of the neck, the spinal

canal is narrowed in its anterior-posterior diameter by anterior buckling of

the posterior-lying ligamentum flavum. In persons with cervical

osteoarthritis, the ligamentum flavum is hypertrophied and the vertebral

canal is narrowed more than it is normally on neck extension; in

combination with the canal narrowing caused by posterior intervertebral

disk protrusion, this may be enough to cause pressure on the ventral or

dorsal surface of the cord. Lhermitte's symptoms presumably are caused by

traumatic depolarization of the sensory tracts. This can happen with neck

flexion as well, since the spinal cord is stretched (potentially depolarizing

irritated nerve fibers). Lhermitte initially described this symptom in patients

who had multiple sclerosis involving the cervical spinal cord. In this

situation, neck flexion that stretches the spinal cord probably causes

symptomatic depolarization in the dorsal column or spinothalamic tracts

made irritable by a demyelinating plaque or other lesion (e.g., neoplasm or

syrinx). In general, a physician should suspect an extramedullary lesion (i.e.,

pressure on the outside of the cord) if Lhermitte's symptom is elicited by

extension of the neck and an intramedullary lesion if elicited by flexion.

A useful maneuver for corroborating your suspicions of root irritation by

posterior lateral protrusion of degenerated disk material is for you to extend

the patient's neck and then press the head firmly downward, thus narrowing

already narrowed spinal foramina. Frequently this elicits the patient's

symptoms and thus corroborates suspicions. More marked foraminal

narrowing can be elicited by extending the head and then flexing it to left or

right. On pressing the head inferiorly (Spurling's maneuver), further

foraminal occlusion occurs on the side to which the head is flexed (Fig. 1-4).

Direct pressure on the posterior lateral part of the neck with the thumb or

index finger may also produce discomfort over the involved roots. Of course,

any forced movement of the neck should be done cautiously in patients with

possible spinal cord injury or injury to the cervical spinal column. Only

enough force should be used to elicit the sign or symptoms and, in the case

of acute injury it may be necessary to perform x-rays before any such

maneuver.

Extremities

Movements of the lower extremity beyond a certain point will stretch lumbar

plexus and nerve roots. Straight leg raising (i.e., passive flexion of the

straightened leg on the hip), or the reverse, extension of the leg on the hip,

is used to indicate the presence or absence of irritative or destructive

lesions involving the lumbosacral plexus and roots. When the leg is flexed on

the hip, the posterior-lying sciatic nerve, which originates in the lower

lumbar and upper sacral roots (L4-S2), is stretched and therefore also

stretches the plexus and roots (Fig. 1-5A). This stretching usually begins

after about 30 degrees of flexion. Extension of the leg on the hip (with the

patient lying on the side or prone) stretches the anterior-lying femoral

nerve, which originates from the middle lumbar roots (L2-4) (Fig. 1-5B).

Any mass or inflammatory process impinging on the nerve, plexus, or

roots is likely to bind or irritate these structures and cause pain in the

peripheral distribution of the nerve. This pain is often in the muscle and

bone distribution of the nerves as opposed to the skin or dermatomal

distribution. Buttock, posterior thigh, calf, as well as heel discomforts are

characteristic of sciatic system involvement, whereas groin and anterior

thigh pains are characteristic of femoral system involvement. If there is skin

involvement, loss of sensation occurs in appropriate dermatomes or

peripheral nerve distribution. However, loss of sensation or weakness will

only occur if the lesion is destructive. Paresthesias (pins-and-needles

sensations) are more common symptoms of dermatomal involvement than is

actual loss of sensation. A symptomatic irritative lesion may not cause any

actual loss of nerve function.

Low-back pain with or without radiation to the leg or legs is the most

common cue for the physician to do the straight leg raising test. A common

cause of low-back pain is lumbosacral disk disease and, if pain radiates into

the leg, a herniated disk is usually the cause. Ninety-five percent of involved

disks are between the L4-5 or L5-S1 vertebral bodies. Therefore, because

the L5 and S1 roots exist at these spaces, straight leg raising with the

patient supine, causing sciatic stretch, is the maneuver of choice. Four

percent of lower spine disk problems occur at L3-4 or L2-3, whereas the

remaining 1% incidence is shared by L1-2 and thoracic disks. With the

higher lumbar protrusions, femoral stretching is the maneuver of choice.

Positive test results reproduce or increase the patient's complaints of leg

pain. An increase of back pain, alone, is not considered an indication of

nerve root involvement and is considered a negative straight leg raising test.

Such a "negative test" may still cause pain, but this is from stretching

irritated tendons, joints and muscles in the back. Also, a true positive test

must be distinguished from tightness of the hamstring muscles, which can

produce discomfort during straight leg raising.

Acute or chronic arthritis of the hip, on occasion, causes referred pain in

the knee and, less commonly, in the foot. Straight leg raising may irritate a

damaged hip joint and may give a misleading impression of sciatic root

irritation. This can be detected by rotating the femur on the hip while the

knee and hip are flexed. This flexion of the knee puts slack on the sciatic and

femoral nerves (Fig. 1-6). Pain caused or increased by this maneuver

(Patrick maneuver) suggests hip disease, and appropriate x-rays can confirm

this suspicion.

Flexion of the head on the chest (chin on chest) pulls the spinal cord

upward and stretches the lumbosacral roots somewhat. Lumbosacral root

irritation may therefore be increased, causing reproduction or exacerbation

of the patient's low back and leg pain. This maneuver would not change the

symptoms of hip disease.

Meningitis manifests itself throughout the subarachnoid space, and

therefore straight leg raising has positive results because the lumbosacral

roots and investments are inflamed. In fact, there may be involuntary flexion

of the knees during attempted straight leg raise (Kernig sign). This can

easily be inferred from our earlier discussion of Brudzinski sign.

Spine

Pathologic processes (degenerative, neoplastic, or inflammatory) in or near

the spinal column frequently give rise to local muscle spasm and pain. If the

process is unilateral, muscle spasm, presumably the result of direct or

indirect irritation of the dorsal sensory and/or motor branches to the

paraspinal muscles, causes characteristic distortion of the spine in addition

to palpable firmness and tenderness. When the paraspinal muscles contract

unilaterally, they bow the spine laterally; the concave side of the bow

appears on the side of increased muscle tension (Fig. 1-7B). This lateral

bowing is called scoliosis and can be observed most easily when the patient

is erect. Observation is further facilitated by making a mark with a pen on

the palpable top of the dorsal spinous processes of the vertebrae. The only

exception to the rule of contralateral bowing occurs at the lumbosacral

junction where the paraspinal muscles are broadly attached to the sacrum

and the ilium. The bowing occurs to the side of the spasm in this instance

(Fig. 1-7A).

Percussion of the spine to elicit point tenderness is routinely carried out

with the hypothenar portion of the fist. Because a large area is covered with

each blow to the spine and there is diffusion to several vertebral segments,

it is more reasonable to use a percussion hammer and tap each spinous

process. Often this accurately localizes the segments involved.

Abdomen, Pelvis and Rectum

Every general medical evaluation should include examinations of the

abdomen, pelvis and rectum. However, on neurologic evaluation these

examinations are not called for unless the patient cues them by certain

complaints. The most common cue is the complaint of low-back pain with or

without radiation into the legs. Even though disk and spine or paraspinous

disorders are the usual cause of this complaint, several common pelvic

neoplastic disorders give rise to very similar complaints and may be

associated with positive straight leg raising. Carcinoma of the cervix is the

most common form of female pelvic neoplasm. It spreads by local extension

and therefore (by invading the pelvic [lumbosacral] plexus) may first become

symptomatic as low-back and/or leg pain. Carcinoma of the prostate is the

most common male pelvic tumor and also spreads by local extension. Low-

back and/or leg pain may be the symptom that brings a patient for medical

attention. Rectal carcinoma occasionally gives rise to low-back pain because

of spread to and enlargement of local lymph nodes. Rectal and pelvic

examinations are mandatory when low back pain is a complaint, especially in

middle-aged and older adults in the age range when the incidence of

neoplasia increases. The lumbar and sacral spine are also common sites of

metastasis of these cancers and this must be considered in the patient with

a history of cancer or in older individuals with new lower back pain.

Low back pain or, for that matter, bone pain involving all levels of the

spinal axis in women mandates breast examination to rule out carcinoma of

the breast which frequently metastasizes to the spine and other long bones.

Acute, new back pain should give rise to consideration of possible abdominal

aortic aneurysm (often palpable or visible on lumbar x-rays and measurable

by ultrasound). Renal disease should be considered in patients with flank

pain and, particularly, if the pain is colicky.

When urinary or fecal incontinence is present or a complaint, rectal

examination is indicated to evaluate both reflex and voluntary anal sphincter

function.

*The retina is very sensitive to mechanical pressure. You may demonstrate

this by pressing very lightly on the lateral side of one of your eyes. The

depolarization block caused by minimal compression of the retina creates a

blind spot (scotoma) in the contralateral field (i.e., next to your nose). In like

manner, early and poorly visible swelling of the disk margin depolarizes and

blocks the proximate retina and enlarges the physiologic blind spot. The

blind spot represents the retina-deficient optic disk and is routinely plotted

and of fairly uniform size when formal visual fields are studied with a

tangent screen or perimeter (see Chap. 3).

**The mechanism for loss of venous pulsations is presumed to be an increase

in venous backpressure subsequent to intracranial hypertension. It is

presumed that papilledema is a function of the ratio of intracranial (and,

therefore, intravenous) pressure to intraocular pressure; elevation of the

former or depression of the latter is adequate to abolish pulsations and elicit

edema of the disk. For practical purposes, papilledema is almost always the

result of increased intracranial pressure. Increased intraocular pressure

(glaucoma) should delay the appearance of papilledema, and this is so; it can

be the source of some diagnostic confusion.

***In persons with long-standing diabetes mellitus or systemic hypertension,

the blot-like hemorrhages may be present but are usually associated with

other abnormalities of the retina, including hemorrhages of the nerve fiber

layer (flame-shaped or striated), narrowing and atherosclerotic distortion of

the arteries, exudates, capillary aneurysms, and vascular proliferation

(neovascularization).

Chapter 2 - Hemispheric function

The cerebral hemispheres, particularly in large and redundant cerebral

cortical mantle, are the anatomical substrates of the uniqueness of Man. The

cortex of the cerebral hemispheres embodies the higher integrative or

intellectual capacities of man and its expanse in area and neuronal numbers

far outstrips the same parameters of our nearest phylogenetic cousin, the

chimpanzee. The complexity of neuronal ramification and interconnection is

fantastic! It is estimated that there are nine billion neurons in each cerebral

hemisphere and each neuron has between five and ten thousand

interconnections with other neurons neighboring and distant. The

mathematical dimensions are staggering, little short of infinite. The latest

generation of man-made brains, in all their circuit complexity cannot

compare.

The higher integrative functions can be divided into those functions

having diffuse representation in the cortex and those with more focal

representation. Some functions are in both hemispheres and some are

unilaterally represented. Obviously, all of this affects the symptoms

produced by damage to the brain.

Diffuse Bilateral Functions

According to Harold Wolff, diffuse bilateral functions include: "(a) the

capacity to express appropriate feelings, appetites and drives; (b) the

capacity to employ effectively the mechanism of goal achievement (learning,

memory, logic, etc.); (c) the capacity to maintain appropriate thresholds and

tolerance for frustration and failure, and to recover promptly from their

effects; (d) the capacity to maintain effective and well-modulated defense

reactions (i.e., repression, denying, pretending, rationalization, blaming,

withdrawal, fantasy, depersonalization, obsessive compulsive behavior and

bodily reaction patterns involving alimentation, respiration, metabolism,

etc.)." These are the kind of functions that are lost only after diffuse and

bilateral injuries to the brain, such as occur in the dementing disorders.

Dementia is defined as a progressive loss of intellectual and higher

emotional capacities. Many of the early changes in rational and emotional

behavior are nonspecific for cerebral dysfunction; that is, they can be the

reflection of severe psychological stress and disorder not of clear-cut

organic origin but of the psychiatric sphere (which have been termed

"pseudodementia").

Condensing the above further, one can see that man's major intellectual

achievement has been the rational control by inhibitory modulation of the

basic drives of self and species preservation common to all animals: feeding,

fighting, fleeing and procreation. The complexity and variability of these

rational and emotional drives and behavior becomes greater and greater as

one ascends the phylogenetic scale, culminating with man. The

manifestations of functional loss, reversible or irreversible, therefore

become more complex and subtle as the functional anatomy of the nervous

system ascends through phylogeny.

As neuronal diffuse dysfunction becomes more advanced, obvious and

unmistakable changes occur. There are deficits in emotional response, often

with a tendency toward apathy and flatness of affect, alternating with wide

and inappropriate swings of emotional behavior. The latter reflects a loss of

rational inhibitory control of the basic emotional drives mediated by the

limbic system. Defects in learning and memory, particularly the former,

abstract thinking, general information and capabilities, and in judgment are

easily detectible in patients with diffuse bilateral involvement.

It may be difficult to distinguish patients with certain psychiatric

disorders from those with early diffuse cortical degeneration. It may be

impossible to test cognitive functions in patients who are psychotically

depressed or catatonic due to schizophrenia. Fortunately, organic cerebral

hemispheric deterioration frequently uncovers primitive reflexes that can be

elicited without cooperation from the patient. Most of these complex reflexes

occur in infants and are suppressed during normal cortical development.

These reflexes reappear with dementia (that is, they become disinhibited).

There is a long list of regressive reflexes has evolved. The most commonly

sought and elicited are the feeding or mouthing phenomena including

involuntary snouting, sucking, rooting, and biting in response to tactile or

visual stimuli, forced grasping with the hands and the feet, and extension of

the great toe on plantar stimulation (Babinski response).

Patients with dementia often show motor perseveration, inappropriately

repeating the same movement due to loss of ability to inhibit ongoing

activity. This may be observed with repetition of words or ideas (this can

occasionally be seen in normal individuals when fatigued or under emotional

strain). Another manifestation of this perseveration can be seen when

testing resting muscle tone. The patient appears to have an inability to relax,

termed paratonia, when the examiner is attempting to passively move a body

part. This can be quite frustrating to the examiner, since it appears that the

patient is willfully resisting passive movement. This perseveration of tone

can meld into a perseveration of movement as the patient overcomes initial

inertia and gets into rhythm with the examiners testing movements. The

examiner becomes aware of this when releasing the patient's arm or leg and

instead of dropping relaxed to the bed, it continues the supposed passive

movements. These abnormalities of tone, labeled paratonia (or gegenhalten),

can be seen in infants and young children so may also represent a

regression of function. It can be seen in normal individuals, but is much

more common in patients with dementia, and therefore has been included

with other things as a "soft sign" of dementia.

Historically, diffuse hemispheric disease (i.e., dementia) has been

considered to be a progressive and hopeless condition of old age. Twenty

years ago, current knowledge and therapeutics accepted just that attitude

with few fortunate exceptions. Today the number of treatable and potentially

reversible disorders of the cerebral hemispheres is growing although the

majority of cases of dementia are not reversible. Additionally, some of the

previously untreatable dementias are yielding partially to new therapies.

New diseases are not appearing; old entities are being recognized as

treatable with the expansion of etiologically and therapeutically oriented

research in dementia. Obviously, the treatable causes of dementia must take

diagnostic priority though they may be statistically unlikely.

Specific Hemispheric Regions and Structures

Some brain functions are localized to specific hemispheric regions. For

example, there are areas of primary motor and sensory function that are

highly localized. On the motor side, skilled movements (particularly of the

distal upper limbs) of the contralateral side of the body are initiated by the

primary motor cortex in the precentral gyrus. There are areas of highly

localized sensory function, including the somatosensory cortex in the

postcentral gyrus and the visual cortex of the occipital lobe. damage to there

areas can affect the ability to feel things or see things on the contralateral

side of the body. The ability to hear and smell are bilaterally represented,

and therefore are generally unaffected by unilateral brain injury. There are

several more complex functions that lateralize. Included among these

functions are language, handedness and visuospatial orientation and, as

already alluded to above, learning, emotionality, and behavioral inhibitory

control.

Left hemisphere

In 97% of the population language is represented in the left hemisphere,

with little if any contribution from the right hemisphere. Only three in one

hundred people will have significant right hemispheric representation of

speech functions; of those three, two will have significant bilateral

representation of speech, with only one individual having right hemisphere

dominance. It is known that early brain injury (the earlier the better, but

generally before the age of about 4), is associated with transference of

language function to the spared hemisphere. With increasing age and

gradual lateralization and anatomical fixation of speech functions to the left

hemisphere, less and less flexibility remains.

The areas involved in the central organization of language, which is

man's most advanced capability, are appropriately the most advanced and

latest developed neocortical zones. It is not too surprising that this highest

function would localize in the most advanced regions and further still that

this function would tend to utilize the greatest expanse of advanced cortex,

which happens to be, in most, localized on the left. The above is interesting

but grossly speculative.

"Why unilaterality?" might be the next question. No one has proposed a

fully satisfactory answer to this teleological question. It is possible that this

is for efficiency, such that language function does not have to occupy

similarly large areas on both sides of the brain (leaving more cortex for

other functions). However, this is speculative. Man appears to be, with rare

exception, the only animal with significant lateralization of such an

important function (some birds apparently have lateralization of their

singing capabilities).

Handedness correlates fairly closely with language dominance. Ninety

percent of the population is right-handed; of 1,000 right-handed people only

one will be right hemisphere dominant for speech; overwhelmingly, to be

right-handed is to be left brained for language. Ten percent of the

population is left-handed; 7 of 10 left-handed individuals are left-brain

dominant for speech, essentially breaking down the nice speech-handedness

correlations seen in right-handed individuals. The remaining 3 left-handers

will be those with either bilateral representation of speech (2) or with right

hemisphere dominance (1). Functional Magnetic Resonance Imaging (fMRI)

has added the capability to study regional metabolic activities in the brain,

which is adding to and corroborating past findings determined by traditional

methods (see Chap. 23).

We have learned most that we know about speech functions and

localization from disease processes involving the brain. Some minor

contribution has come from stimulation studies and observations of the

effects of drugs. Table 2-1 summarizes the effects of destructive lesions of

the classic anatomical speech areas of Broca and Wernicke. Dysfunctions of

language are called dysphasias, complete loss of some component of

language function is called aphasia.

Testing of the patient with a suspected language disorder requires

several steps. These include: observation of the characteristics of

spontaneous production; response to variably complex commands; the

ability to repeat complex phrases; the ability to name objects and parts of

objects; and the ability to read and write. Testing of these functions will

usually quite accurately localize the area of involvement. The finding of

other areas of cortical damage can also help localize the process, since some

functions are located close to the language areas of the cortex. For example,

a patient with verbal language dysfunction, homonymous hemianopsia and

little motor deficit, will more than likely have a receptive (Wernicke)

dysphasia. A patient with a verbal language dysfunction, marked hemimotor

and hemisensory deficit and no visual abnormality will probably have an

expressive (Broca) dysphasia.

For practical purposes it is worth noting that the majority of patients

with dysphasia will have a combination of both expressive and receptive

dysfunctions (called global dysphasia). This is because the majority of

patients who are dysphasic are so because of cerebral infarction and the

infarction, usually patchy, involves the middle cerebral artery territory,

which encompasses both language areas as well as the pathway connecting

them, the arcuate fasciculus (see Fig. 2-1). Damage to the arcuate fasciculus

can disconnect the area of the brain that comprehends language (Wernicke

area) from the area that is generating language (Broca area). This would

abolish the ability to repeat a complex phrase, since the comprehension of

the phrase could not be transmitted to the area generating the words.

An even more unusual "disconnection syndrome" occurs when the areas

around the primary language areas are damaged, leaving the primary

language areas intact (Fig. 2-2). This "disconnects" the language areas from

the rest of the cortex, which is contributing to the thought processes that

are then being expressed through the primary language areas. Such

individuals would be able to repeat, but would have problem spontaneously

generating meaningful language.

Damage to the entire corpus callosum can cause a very striking

disconnection syndrome (sometimes termed "split brain"), although it may

not be observed unless the proper functions are tested. One of the most

striking features of the fully expressed "split brain" is the inability to

verbally tell you what an article is, if it is placed in the left hand (assuming

left hemisphere dominance and that the patient is prevented from looking at

it). Additionally, this individual will be unable to understand written

language if the writing is presented only to the left visual field. This material

reaches only the right hemisphere and cannot be transferred to the left or

verbal hemisphere, for interpretation.

A rather striking and frequently-quoted example is that of the woman

with corpus callosum transection who snickered when a risqué picture was

presented to her left field. When asked why she laughed her left hemisphere

answered, "It's a funny test." When the picture was flashed into the right

visual field, and therefore seen by the left hemisphere, the patient quipped

"You didn't tell me I was going to have to see this kind of a picture." During

the first presentation of the picture, the right hemisphere saw the picture

and laughed. The left hemisphere rationalized that the laugh must have been

because the test was funny. From the above it is obvious that the right and

left cerebral hemispheres, to some degree, are able to function as two

separate individuals if disconnected.

In addition to having visual transfer problems, transection of the corpus

callosum will prevent transfer of auditory verbal commands from the left

hemisphere to the right. Commands to do chores with the left hand will

therefore be carried out imperfectly or not at all.

These examples and the observation of the patient with a split brain

pulling the pant leg up with the right hand and down with the left (as if the

right and left hemispheres were in competition) reinforce the assumption of

a partial schizo cerebration which comes to light only when the major

connection, the corpus callosum, is destroyed. It is noteworthy that there

may be other connections between the left and right hemisphere, especially

if damage to the corpus callosum occurs early in life (such as agenesis).

Right hemisphere

The right hemisphere must be considered functionally inferior to the left

since it lacks significant speech representation. Therefore it has been

termed the "non-dominant" hemisphere. However, certain functions do tend

to localize to the right hemisphere. For example, the ability to recognize loss

of function, visuospatially oriented perception and behavior, and musicality

all appear to be predominantly functions of the right cerebral hemisphere.

Also, the ability to generate verbal inflections and to detect tone of voice

appears to be localized to the right hemisphere.

The patient with severe right hemispheric dysfunction (e.g., subsequent

to infarction, trauma, hemorrhage, or tumor) will manifest rather obvious

deficits in elementary hemispheric functions: s/he will have a hemiweakness,

hemisensory depression, and various abnormalities of cranial nerve function.

These deficits are not at all surprising based on cortical localization.

However, particularly if the non-dominant parietal lobe is involved, the

capacity to acknowledge or recognize loss is severely impaired; for example,

the patient may not know that there is anything wrong and therefore will

deny the allegation that there is a deficit. When asked to move the left arm

they may say that they have done so even though no visible movement has

occurred. More bizarrely they may reach for the left arm and grasp the

examiner's, which has been slipped in the path, and claim that it is their

own. Also they may deny that their arm actually belongs to them; this

abnormality probably depends to some degree upon the amount of sensory

depression on the left. Some time ago, a patient with severe right

hemisphere dysfunction due to a stroke was examined at the VA hospital.

When turned onto his right side for the purpose of carrying out a lumbar

puncture he vociferously objected to the presence of another person who

was lying on top of him; the other person was his own left side! The term

applied to the lack of appreciation (or neglect) of deficits is "anosognosia" is

the term applied to this deficit. In time, anosognosia fades, compensated by

recovery of right cerebral function or some transfer of this function to the

left hemisphere. However, there are usually some remnants of neglect

unless the pathology completely reverses (e.g., the patient, when asked what

is wrong, might answer, "The doctors tell me I am weak on the left," etc.).

These patients, as you may surmise, tend to be poor rehabilitation

candidates because their neglect decreases their motivation for

improvement. The patient with a similar motor disorder in the right limbs

from left hemispheric damage, despite the fact that they may have severe

language deficits, is quite conscious of the motor loss and quite willing, even

insisting, to rehabilitate him- or herself.

Lesions of the right hemisphere, particularly when they involve the

confluence of the parietal, occipital and temporal lobes are frequently

associated with visuospatial disorientation of a disabling degree. This can be

tested at the bedside by having the patient fill in well-known cities such as

San Francisco, New York and Washington on a map of the United States or

by having the patient copy a two dimensional rendition of a cube. At a

practical level, visuospatial disorientation creates problems with following

directions, reading maps and when an unfamiliar place is encountered

navigation may become grossly disordered. Penfield described a patient,

who after right temporal lobectomy was lost as soon as he lost sight of

home. he was forced to take a job in the post office across the street from

home in order to avoid daily confusion (Fig. 2-3).

Musicality is also a predominance of the right hemisphere. Lesions,

particularly of the temporal-occipital-parietal confluence on the right, cause

variable deficits in tune learning and reproduction. Left-sided destruction

can leave the patient without speech but musical ability will frequently

remain intact with the patient readily and correctly reproducing tunes if s/he

is cued by the examiner.

Frontal lobes

The frontal lobes include the areas of the motor cortex and the premotor

cortex posteriorly, and the prefrontal cortex anteriorly. The motor and

premotor cortices are involved in the planning and initiating of movements.

Damage to medial areas of the premotor cortex (supplementary motor area)

can prevent the ability to initiate voluntary actions (abulia) that can be so

severe as to prevent any movement (akinesia). Additionally, Broca area is

part of the premotor cortex in the dominant hemisphere.

The prefrontal cortex has more complex functions. Broadly, we divide

this part of the cortex into dorsolateral prefrontal cortex and the

orbitomedial prefrontal cortex. The dorsolateral prefrontal cortex is involved

in what has been called executive functions. Osborn described these

functions as: "The ability to organize thoughts and work, to create plans and

successfully execute them, to manage the administrative functions of one's

life. Individuals with impaired executive function may appear to live

moment-to-moment, fail to monitor their activities or social interactions to

make sure plans are carried out (or even made). With diminished ability to

create strategies, to handle more than one task at a time, to be effective,

reliable, and productive, the simplest job may be too challenging." Damage

to this area also can affect "working memory" which is the ability to hold

something in the mind while manipulating it (such as repeating a string of

numbers backward) and also inhibits the ability to perform several tasks

simultaneously.

The orbitomedial prefrontal cortex is involved in control of impulses and

behavior. Damage to this area severely affects personality. Patients display

poor judgment, inadequate planning, and little motivation. With more

advanced disease, they may become inappropriately jocular ("Witzelsucht")

and irritable and lose their social graces. It has been proposed that the

orbitomedial prefrontal cortex is anatomically situated (in terms of their

connections) between the perceptual motor systems of the hemispheres and

the limbic system. Lesions in this area might then divorce perception and

action from motivation. A classic example of this was described by Harlow

after prolonged observation of a patient, Phineas Gage, who had sustained

severe damage to the orbitomedial prefrontal cortex. “The equilibrium or

balance, so to speak, between his intellectual faculties and animal

propensities, seems to have been destroyed. He is fitful, irreverent,

indulging at times in the grossest profanity (which was not previously his

custom) manifesting but little deference for his fellows, impatient of

restraint or advice when it conflicts with his desires, at times pertinaciously

obstinate, yet capricious and vacillating, devising many plans of future

operation, which no sooner arranged than they are abandoned… in this

regard his mind was radically changed, so decidedly that his friends and

acquaintances said that he was ‘no longer Gage.’”

There are a variety of physical findings that are common, but not

specific, for prefrontal cortex lesions. Grasp, sucking and snout reflexes are

common. Paratonia (gegenhalten) and perseveration of actions or speech are

often seen. As described above, paratonia (gegenhalten) refers to an

increase in tone; instead of relaxing, the patient either resists or tries to

help when the examiner attempts to move the limbs passively. Perseveration

refers to the repetition of a response when it is no longer appropriate. A

person may raise their hand on command, for example, and then continue to

raise their hand when asked to point to the floor or touch the nose. Verbal

responses can similarly demonstrate perseveration.

Perseveration may occur for a variety of reasons: inability to make the

correct response, failure to check the response against the question, or lack

of attention to the task. However, it may also be an inability to terminate or

change ongoing motor activity or postures. This has been considered more

likely to occur with loss of the inhibitory influences of the frontal lobes.

A number of tests have proved sensitive to the akinesia of patients with

frontal lobe disease, and to their tendency to persist in incorrect behavior

even when they know they are wrong. A test of word fluency can easily be

given at the bedside. The patient is asked to produce as many words as they

can that begin with a given letter (excluding proper nouns) in a one minute

period. Normal individuals can produce 14 +/- 5, words using the letters A,

F, or S. Patients with left frontal lobe lesions produce fewer words, and

often repeat words or persist in using proper nouns.

Limbic system

The limbic system, in addition to subserving higher emotional functions,

appropriately subserves a major component of the memory system,

declarative memory (memory for facts or relationships that can be expressed

verbally or symbolically). The ability to imprint new material (short term

memory) is lost with bilateral destruction of most of the major paired

structures of the limbic system including the cingulate gyri, hippocampi (and

adjacent medial temporal lobes), fornices, mammillary bodies and anterior

and medialis dorsalis nuclei of the thalamus. The patient with these lesions

will be able to retain material as long as they are concentrating on it; this

attentive or immediate memory probably depends upon the integrity of the

major sensory pathways, the reticular activating system of the upper

brainstem and the dorsolateral prefrontal neocortex. If, however, attention

is distracted, s/he will have difficulty or be unable to recall the presented

material. In fact, the patient may ask, "What three words?" when asked to

reproduce three unrelated words such as table, red, 23 Broadway after a

period of distraction.

There are several conditions that can produce isolated bilateral

depression or destruction of limbic structures involved in short term

memory. For example, it can occur as the result of herpes simplex

encephalitis, bilateral posterior cerebral artery occlusive disease or may be

the result of unilateral temporal lobectomy if the patient has a previously

damaged (e.g., from birth trauma) contralateral temporal lobe. Bilateral

temporal lobe involvement may be an early and prominent sign of

Alzheimer's disease. The limbic system is also much more susceptible to

metabolic insults such as hypoxia and thiamin deficiency, the latter being

most often seen in malnourished alcoholics. In the case of alcoholic effects

on the brain, which probably result from bilateral damage to the

dorsomedial nucleus of the thalamus, the memory deficit may be

accompanied by confabulation (a tendency to respond to memory tasks by

"making up" plausible answers).

Of course, if things cannot be remembered over minutes to hours, they

can not be remembered long-term. However, well-learned material is

probably represented diffusely and is very resistant to focal destruction.

Indeed, well-established memories fail last in patients with diffuse bilateral

hemispheric dysfunction. Animal experiments suggest that intermediary or

less well-established material is first stored in the temporal lobes and

becomes more widespread or redundant in localization with reinforcement.

Some clinical corroboration of this is seen in patients with bilateral temporal

lobe lesions who have variable and patchy retrograde amnesia.

When testing a patient for problems with learning and memory, it

suffices to ask for:

1. reproduction of three unrelated words immediately and then after a

period of distraction;

2. a description of recent past events, for example front page news

items, the contents of breakfast (if not stereotyped fare) and what they

have been doing recently (assuming that the examiner knows the

answers to these questions); and;

3. a description of some well learned past material such as the past 4 or

5 presidents, birth dates of patients and family, anniversaries, number

and location of children and grandchildren, etc.

 

References

Benson, DF. Aphasia, Alexia, and Agraphia. New York, Churchill

Livingstone, 1979.

Geschwind, N. Selected papers on Language and the Brain. Boston,

Reidel, 1974

Vinken PJ and Bruyn, F.W. (eds). Disorders of speech perception and

symbolic behavior, in: Handbook of Clinical Neurology, Vol. 4. New

York, John Wiley & Sons, 1969.

Questions

Define the following terms:

agnosia, agnosagnosia, apraxia, receptive aphasia, expressive

aphasia, global aphasia, alexia, agraphia, dysinhibition, dysnomia,

paraphasic, paratonia, perseveration.

Agnosia is the inability to recognize what something is despite being able to perceive it.

This can be visual, auditory or tactile.

Agnoagnosia is the inability to recognize a particular deficit (for example that one is

paralyzed).

Apraxia is the inability to synthesize a complex motor pattern despite having the strength

and coordination to perform it.

Receptive aphasia is the inability to understand language (written or verbal).

Expressive aphasia is the inability to synthesize language (written or verbal).

Global aphasia is the inability to either understand or to synthesize language (written or

verbal).

Alexia is the inability to read.

Agraphia is the inability to write.

Dysinhibition is the appearance of responses that are normally suppressed. In the context

of higher cognitive functions, it is the return of more primitive reflexes or behavior

patterns that are normally suppressed by "higher areas" of the brain (often the frontal

lobe).

Dysnomia is the inability to name objects.

Paraphasic errors include substituting words that have inappropriate meaning, although

the words sound somewhat similar or start with the same sounds. This often happens with

receptive aphasias.

Paratonia is and involuntary, irregular resistance to passive movement (it feels like the

patient is assisting in movement when they are not attempting to).

Perseveration is repeating motions (or responses) when it is inappropriate to do so.

2-1. Name some cerebral cortical functions that are well localized and

unilateral. (unilaterally or bilaterally) and some that are diffuse.

Answer 2-1. Well localized, unilateral cortical functions include: somatic sensation,

voluntary motor function (especially of hands), expressive language, receptive language,

attention to the contralateral world (neglect), understanding of what is wrong

(agnosagnosia), vision.

2-2. Name some cerebral cortical functions that are well localized and

represented bilaterally.

Answer 2-2. Well localized and bilateral cortical functions: hearing, short term memory,

frontal lobe functions (mood, behavior, emotional control, motivation, executive

functions), visuospatial function (parietal lobe)

2-3. Name some cerebral cortical functions that are diffusely represented in

the cerebral cortex.

Answer 2-3. Diffuse cerebral cortical functions: long term memory, self and species

preservation functions (including many behavioral functions.

2-4. Damage to which cerebral cortex produce aphasia?

Answer 2-4. Aphasia is lateralized to the dominant hemisphere

2-5. What can you say about the ability to write in patients with aphasia?

Answer 2-5. Patients with aphasia will write and read the same way that they speak and

comprehend speech, respectively.

2-6. What can you say about the ability of a patient with expressive receptive

or global aphasia to repeat complex phrases?

Answer 2-6. Patients with expressive, receptive or global aphasia will be unable to repeat

complex phrases.

2-7. What can you say about the ability of a patient with transcortical

aphasia to repeat complex phrases?

Answer 2-7. Patients with transcortical aphasia will be able to repeat although they may

not be able to name objects that are presented to them or to understand language.

2-8. What problems will a patient with a transcortical aphasia have?

Answer 2-8. Transcortical aphasia: will be able to repeat complex phrases but will either

be unable to understand complex statements or commands (transcortical receptive) or be

unable to come up with names for objects (transcortical motor).

2-9. What are the characteristics of the patient with an expressive aphasia

(Broca's).

Answer 2-9. Epresssive aphasia: Brocca's area, nonfluent, frustrated, dysnomic, can read

and understand speech, telegraphic speech.

2-10. What are the characteristics of the patient with a receptive aphasia

(Wernicke's).

Answer 2-10. Receptive aphasia: Wernicke's area, fluent, not frustrated, dysnomic, can't

read or understand complex speech.

2-11. What is the most common lesion to produce alexia without agraphia

(can write but can't read)?

Answer 2-11. Damage to the dominant occipital lobe and splenium of corpus callosum can

produce alexia without agraphia (can write but can't read).

2-12. What area is involved in immediate recall (for example of a phone

number).

Answer 2-12. Immediate recall is a frontal lobe effect (give back a phone number).

2-13. What area is involved in short term memory?

Answer 2-13. Short term memory is a hippocampal function (minutes).

2-14. Where is long-term memory stored?

Answer 2-14. Long term memory is stored diffusely (only lost if large and diffuse areas are

damaged).

2-15. What are "executive functions" and where are they primarily located?

Answer 2-15. Executive functions in dorsolateral perfronal part of frontal lobes - these

include sequencing, planning, immediate recall, abstractions.

2-16. Where are the areas involved in most of emotional control and

"personality"?

Answer 2-16. The orbital and medial frontal (and anterior cingulate) cortex are involved in

emotional control.

2-17. Damage to which hemisphere is more likely to produce depression?

Which will more likely produce mania?

Answer 2-17. Left frontal damage often produces depression, right frontal may lead to

mania.

2-18. Neglect of one side of the world is most commonly due to damage to

what area?

Answer 2-18. The parietal lobe is responsible for attention to contralateral world (damage

produces neglect) and knowledge of deficits.

2-19. Agnosagnosia most often results from damage to what area?

Answer 2-19. Agnosagnosia, a lack of recognition of problems, is due to damage to the

parietal lobe (especially the non-dominant side).

2-20. What "primitive responses" would be expected to be uncovered by

damage to the frontal lobes?

Answer 2-20. disinhibited glabellar, snout, suck, palmomental and grasp reflexes.

2-21. Paratonia is a sign of what?

Answer 2-21. Paratonia results from diffuse cortical dysfunction (some degree may be

normal).

2-22. What would you expect to see in the patient with a split corpus

callosum?

Answer 2-22. Corpus callosum lesions may prevent information from transferring from

one hemisphere to the other. The "left hand does not know what right hand is doing."

2-23. The neocortex provides inhibitory modulation of what four basic

drives?

Answer 2-23. Feeding, fighting, fleeing and procreation (the four F's).

2-24. What is the clinical term used to describe diffuse hemispheric disease

(one word)?

Answer 2-24. Dementia.

2-25. What are the clinical signs of advanced dementia?

Answer 2-25. Loss of cognitive, intellectual functions in more than one sphere of function.

2-26. What regressive reflexes emerge with loss of cortical inhibition?

Answer 2-26. Dysinhibition of glabellar response, palmomental reflex, grasp reflex, suck

reflex, rooting reflex, snout reflex and loss of nuchocephalic reflex.

2-27. What what are the functions of the limbic areas of the brain?

Answer 2-27. Self and species preservation functions, the "four F's" and emotional

reactivity.

2-28. Of 100 people, how many will have significant R hemispheric

representation of speech functions? Of these, how many will have bilateral

speech representation?

Answer 2-28. 1% right dominant and 2% mixed.

2-29. What percentage of R-handed people are L-hemisphere dominant for

speech?

Answer 2-29. About 99.9%.

2-30. What percentage of L-handed people are L-hemisphere dominant for

speech?

Answer 2-30. About 70%.

2-31. Below what age can speech function be recovered if the dominant

hemisphere is damaged?

Answer 2-31. Age four.

2-32. What are dysfunctions of speech called? What is a complete loss of

speech called?

Answer 2-32. Dysphonia (if hoarseness due to mechanical problems in larynx), dysarthria

(if due to problems with cranial nerves or cerebellum) or aphasia (this is actually a

language problem, not just speech problem). Dysphasia is incomplete, aphasia complete

loss of language function.

2-33. A patient with verbal language dysfunction, homonymous

hemianopsright visual field deficit and little motor deficit most likely has

what type of dysphasia?

Answer 2-33. Receptive (Wernicke's) - this is because Wernicke's area is closer to the

parietal lobe (and the optic radiations).

2-34. A patient with verbal language dysfunction, marked hemimotor and

hemisensory deficit, and no visual abnormality most likely has what type of

dysphasia?

Answer 2-34. Expressive (Broca's) - this is because Broca's area is closer to the motor

cortex.

2-35. Where is Broca's area located? Where is Wernicke's area located?

Name the fasciculus that links the two of them.

Answer 2-35. Broca's - Inferior frontal lobe, just anterior to motor cortex and near Sylvian

fissure; Wernicke's - posterior part of superior temporal gyrus; the arcuate (superior

longitudinal) fasciculus connects these language areas.

2-36. What gyrus is important in language, especially in word retrieval?

Answer 2-36. Angular gyrus.

2-37. Do most patients with dysphasia have Broca's, Wernicke's, or a

combination of both? Why is this so?

Answer 2-37. Combination because they are in same vascular distribution on same side.

2-38. What language abnormalities are manifested with a lesion to Broca's

area? Wernicke's area? Angular gyrus? Arcuate (superior longitudinal)

fasciculus?

Answer 2-38. Broca's - expressive aphasia; Wernicke's - conductive aphasia; Angular -

dysnomic aphasia; Arcuate fasciculus - conductive aphasia.

2-39. What part of the corpus callosum transfers COMPLEX [i.e., verbal]

visual info between the two hemispheres?

Answer 2-39. The splenium.

2-40. What are the predominant functions of the R cerebral hemisphere?

Answer 2-40. Visuospatial functions, attention to contralateral world, musicality.

2-41. Which patient will be more motivated to recover from a hemispheric

lesion, one with damage on the L or the R?

Answer 2-41. The left (the right hemisphere lesion can result in a lack of appreciation for

deficits and therefore problems in compensating).

2-42. Where is the location of a lesion that causes visuospatial

disorientation? How does this manifest itself?

Answer 2-42. Right parietal lobe. Patients may get lost and have trouble assembling

things or figuring out how to make them work.

2-43. What type of lesion will result in the loss of the ability to imprint new

information?

Answer 2-43. Hippocampal lesions - medial temporal lobe (bilaterally).

2-44. Can well-learned material be easily destroyed by a focal lesion? Why or

why not?

Answer 2-44. No, there is diffuse representation.

2-45. What three categories of questions need to be asked when testing a

patient for problems with learning and memory?

Answer 2-45. Immediate recall; short term recall (several minutes after distraction); recall

of remote events.

2-46. What evidence would lead to the conclusions that a demented patient

has disease localized primarily in the frontal lobes (i.e., what are the

manifestations of lesions to the frontal lobes)?

Answer 2-46. Emotional lability, personality change and/or loss of executive functions.

2-47. What is the effect of lesions localized to the medial aspect of the

frontal lobes (parasagittal frontal cortex - supplementary motor area)?

Answer 2-47. Inability to initate movements (abulia).

* The patient is stood or seated with eyes closed in front of the examiner.

The examiner rotates the patient's shoulders. The uninhibited response

consists of the patient's head remaining straight.

Chapter 3 - Olfaction and Vision

Vision and olfaction are two of the special senses. While patients usually

easily recognize loss of vision, loss of olfaction may not be recognized

without testing.

I. Olfaction

Unilateral depression or loss of olfaction (anosmia) is most commonly due to

obstruction of the nasal passages. When it is due to damage to neural

structures, it must affect the olfactory pathway at or rostral to the olfactory

trigone (Fig. 3-1). Therefore, dysfunction must be in the olfactory tract,

bulbs, nerve filaments, or olfactory mucosa in the roof of the nasal passage.

Olfactory pathway

The olfactory pathway divides immediately anterior to the anterior

perforated substance to travel via (1) the lateral olfactory stria to the

primary olfactory cortex (prepiriform-piriform) in the ipsilateral mesial part

of the temporal lobe, (2) the anterior limb or stria that dives into the

anterior perforated substance to join the anterior commissure, which carries

it to the contralateral olfactory cortex, and (3) the medial olfactory stria,

which travels medially from the trigone to distribute to limbic cortex in the

septal, subcallosal, and parasagittal frontal regions.

Damage to the olfactory epithelium, the olfactory filiments, the olfactory

bulb or olfactory tract can cause unilateral anosmia. Destruction of olfactory

cortex or olfactory pathways posterior to the trigone (where the tracts

divide) must be bilateral to depress olfactory function. Potentially irritative

lesions (tumor, post-traumatic or ischemic scarring, arteriovenous

abnormalities, etc.) in the olfactory cortical regions may be the source of

epileptic activity and cause olfactory symptoms; that is, the patient may

complain of hallucinations of smell. Typically, these olfactory hallucinations

are described as acrid and unpleasant and are not lateralized by the patient.

Testing of olfaction

Olfaction is tested by having a patient with eyes closed, sniff a relatively

familiar odor from a small vial, occluding the nares alternately to test each

side separately. Substances such as acetic acid and ammonia should not be

used for testing because they cause strong trigeminal stimulation and can

therefore be sensed by an anosmic person. Coffee grounds are popular

because they are recognized by approximately 80% of normal individuals

and cause minimal trigeminal stimulation. Three distinct levels of function

can be determined: (1) cannot smell, (2) can smell something, and (3)

recognizes coffee. In addition, a person may recognize an asymmetry of

sensitivity despite an inability to recognize the substance. Lack of

recognition is not significant if the patient responds by saying that they

smell a substance bilaterally; recognition on one side suggests contralateral

hyposmia if the patient claims to smell but not recognize something on the

opposite side.

Disorders affecting olfaction

Examples of disease processes that cause or are associated with decreased

or otherwise abnormal smell are as follows:

1. Mechanical.

o a. Common cold with occlusion of nasal passages (most common

cause of hyposmia).

o b. Unilateral occlusion by deviated nasal septum.

o c. Occipital head trauma with shearing effect on olfactory nerve

filaments passing through cribriform plate (Fig. 3-2).

o d. Frontal head trauma, if it results in a fracture line through the

cribriform plate, causes anosmia by tearing the fine olfactory nerve

filaments. (In the absence of fracture, frontal head trauma is less likely to

cause hyposmia.)

o e. Tumors (most commonly meningioma) on the mid-portion of the

sphenoid ridge or in the olfactory groove, both capable of pressing on the

olfactory tract. If the tumor is on the sphenoid ridge so that, in addition to

pushing up on the olfactory tract, it compresses down on the optic nerve, it

causes the syndrome of ipsilateral anosmia, optic atrophy, and possibly

also contralateral papilledema because of increased intracranial pressure

caused by the tumor mass effect (Foster-Kennedy syndrome).

2. Metabolic.

o a. Pernicious anemia (vitamin B12 deficiency) is frequently associated

with bilateral decreased olfaction.

o b. Vitamin A deficiency is associated with hyposmia and dysosmia

(odors are unpleasant), possibly the result of nasal mucosal abnormalities.

o c. Zinc deficiency has been associated with hyposmia and dysosmia.

o d. Diabetes mellitus. Presumably, this hyposmia is secondary to

demyelination in the olfactory tracts or loss of the peripheral olfactory

neuron.

o e. Multiple sclerosis is a rare cause of hyposmia, presumably on the

basis of olfactory tract demyelination.

o f. Herpes simplex encephalitis, which tends to localize in the temporal

lobes and cause severe hemorrhagic necrotic destruction, may cause

anosmia secondary to bilateral olfactory cortex destruction or

alternatively, because the virus may enter the nervous system via the

olfactory mucosa, may destroy one or both olfactory nerves and bulbs in

the process. The presentation of acute-onset anosmia and a severe

memory-encoding deficit (the latter secondary to bilateral mesial temporal

lobe destruction) in a person who is febrile suggests the possibility of

herpes simplex encephalitis, a treatable disorder.

o g. Hepatic disease, particularly acute hepatitis, is frequently

associated with an unpleasantness of odors (dysosmia).

Unilateral destructive or compressing (mass) lesions in the anterior

temporal lobe may cause olfactory hallucinations, a focal epileptiform

discharge that often spreads to involve other portions of the limbic system

and neocortex (see Chap.13).

II. Vision

For a more detailed elaboration of visual system anatomy and function, refer

to a neuroanatomy text. Figure 3-3 shows diagrammatic representations of

the visual pathway including expected abnormalities of vision caused by

lesions of its various parts.

Visual deficits

Unilateral lesions of the retina and optic nerves cause monocular defects.

Lesions from the chiasm back give rise to binocular field defects because of

crossing of the nasal half of the retinal fibers from each eye. An exception to

this rule occurs when there is involvement of the fibers representing the

nasal retinal (temporal field) peripheral crescents. The fibers from this

portion of the retina have no homonymous counterpart in the opposite

peripheral temporal retina (nasal field). The peripheral crescents, therefore,

remain monocular in representation from the retina to the visual cortex

(Figs. 3-3, 3-4 and 3-5).

Testing of vision

Formal testing of vision divides this function into two basic aspects: (1)

central or cone vision, and (2) peripheral or rod vision. Peripheral vision is

the greatest part of the visual field, whereas central vision represents a

relatively small segment of the projected visual world. Nevertheless, it is

mainly central vision that is responsible for visual acuity and color vision.

However, cones require a lot of light in order to function effectively.

Peripheral vision also subserves a major function of directing central vision

by visual-oculomotor responses toward the peripheral stimuli. The more

peripheral the field, the less capable of form or figure perception it becomes,

which is in keeping with the centrifugal thinning out of the population of

peripheral field receptors (rods) in the retina. At the far periphery one is

capable of perceiving only moving objects, although reflex movements of the

eye (directing the eyes toward a moving stimulus) can be elicited from this

region. Rods have a very low threshold for activation by light as compared

with cones and are thus more suited for night vision. In daylight, pigment

"bleaches" and the rods are insensitive. The cones, which have a high

threshold for pigment bleaching by light, are relatively useless in the dark.

Visual acuity

Visual acuity is first tested by having a person read a chart (Snellen chart)

containing standard-sized figures (numbers, letters or other forms) as

perceived at a standard distance. The notation 20/20 vision means that the

patient can recognize objects at 20 ft. that a normal person can recognize at

that distance. The designation 20/70 means that the patient, at best, can

only recognize at 20 feet what abnormal individual can recognize at 70 feet.

This type of testing is not practical at the bedside, so charts have been

developed to be presented at 14 in. (Fig. 3-6). These give an extrapolated

visual acuity in terms of 20 ft. and are adequate to detect neurologic visual

dysfunction, but may miss refraction errors, particularly nearsightedness

(myopia). For quick screening, it is useful to know that recognition of small-

case newsprint at 14 in. is equivalent to 20/30 vision.

Visual acuity can be depressed by changes in the refractive structures of

the eye anterior to the retina. In neurologic practice, we are not concerned

with refractive problems and, therefore, it is important to have a way to

detect these causes of loss of visual acuity. If a person customarily wears

glasses, s/he should be tested with them on. If difficulties still exist, then

further testing is warranted. Ophthalmoscopic examination should detect

corneal opacities or cataracts. It would also detect intraocular problems,

such as hemorrhage, which could obscure vision. Refractive errors

commonly affect visual acuity. However, conditions such as myopia (near-

sightedness) or hyperopia (far-sightedness) can be corrected with a series of

lenses. Alternatively, at the bedside, most simple refractive errors can be

corrected by having the patient look through a cluster of pin-holes (Fig. 3-7).

This works by only permitting parallel light rays to pass the pin-hole. This

markedly increases the dept of focus since parallel rays do not have to be

focused. Pinholes would make inexpensive but impractical glasses, however,

because peripheral vision, most central vision, and a great amount of light

are eliminated. If visual acuity is not substantially corrected by the pinhole

and if no problems exist with the refractive media of the eye (on

ophthalmoscopic examination), it can be assumed there is a neurological

(i.e., cone system) central visual defect.

A further way to estimate refractive errors, which is particularly useful

in the uncooperative patient, is to determine the diopters (e.g., +3, -3) of

ophthalmoscope adjustment necessary to focus on the macula or optic nerve

head. This assumes "0" to be equivalent to normal acuity.

Visual field

After determining that the visual deficit is not a refraction or occlusive

problem one can deduce, by default, it is a dysfunction in the neural visual

apparatus. In order to localize the lesion, it is necessary to evaluate the

visual field integrity. Visual field loss tends not to be an all-or-nothing

phenomenon. The patient frequently has a partial deficit, particularly in the

central field, and can see larger objects after small objects are no longer

perceived. Testing that utilizes small objects is more sensitive.

Formal testing of visual field can be done in several ways. There are

automated tests, such as "Goldman visual field testing" in which the patient

is asked to push a button when a flash of light is detected. "Tangent screen"

testing is an older method in which the patient fixates on a central target at

a distance of 3 meters while objects are moved into the screen. Of course,

each eye has to be tested independently (Fig. 3-8).

At the bedside, "confrontation" is the most commonly employed method

for evaluating visual field. This can be quite accurate if carefully done. One

eye is covered and the person is asked to fix their vision on the examiner's

pupil at a distance of approximately 1.5 ft. A small, colored object (for

example a 3 mm red object such as a fireplace match) is moved into the

visual field in a plane halfway between the patient and the examiner. The

patient is asked to indicate when s/he sees the object and when it turns red

as well as whether it disappears or loses its color anywhere in the field. This

technique allows the examiner to compare the patient's vision with their

own (presumably normal). Additionally, it is critical to observe whether the

patient is fixating on the central object (i.e., examiner's pupil) during the

examination. A colored object is used because it defines the major extent of

cone vision. On occasion, a partial loss of central vision manifests itself more

in depression of color perception than in actual loss of visual acuity. For

example, optic neuritis often diminishes the ability to see red objects ("red

desaturation"). Screening to test all peripheral quadrants with both of the

patient's eyes open and fixating on the examiner's nose reveals all

peripheral defects except the rare cases of nasal hemianopias and

hemianopias with temporal crescent sparing (see Figs. 3-3 and 3-4).

Monocular testing does not miss any peripheral defects but takes twice as

long.

If there has been damage to optic nerve fibers for more than a couple of

weeks, ophthalmoscopic visualization of the optic disk may reveal evidence

of "atrophy" of the temporal portion of the optic nerve head (optic disk). This

part of the optic disk transmits the optic nerve fibers from the macula

(representing central vision). Atrophy causes the disk to change from its

slightly yellowish appearance to a brighter white owing to gradual

replacement of myelinated nerve fibers by glial scarring. Comparison with

the opposite disk is useful in borderline cases when changes are minimal

and the problem is monocular.

There is a normal, oval scotoma (the "physiologic blind spot") in the

temporal portion of the visual field (see Fig. 3-8). This is the visual

representation of the optic nerve head (the disk), which does not contain

rods or cones. When a 3 mm object is passed over this area, a person usually

says it disappears. It is often helpful to suggest to the patient that the object

will likely disappear in some part of the visual field since most of us are

completely unaware of the presence of a blind spot. If the object is moving

midway between the examiner and the patient and both are fixating on each

other's pupils, their blind spots should be superimposed. The ability of the

test to pick up the physiologic blind spot is a good check on the reliability of

the mode of testing of the visual field.

An early sign of edema or swelling of the optic disk (papilledema) is

enlargement of the blind spot. This is because the retina is extremely

sensitive to mechanical pressure and minimal, unobservable edema of the

optic nerve head causes significant dysfunction in the bordering receptive

retina and, therefore, enlargement of the blind spot. Also, glaucoma will

tend to push out on the optic disk, producing expansion of the optic cup (at

the center of the disk) and also some expansion of the blind spot. More

severe glaucoma can destroy the retina thorough pressure.

Peripheral visual fields are formally tested using the tangent screen

(Fig. 3-8) and more completely using a perimeter (Fig. 3-9), which takes into

account that the total visual field is an arc (see Fig. 3-5). A tangent screen is

flat and so cannot demonstrate the total extent of the peripheral visual field.

A relatively large, white (color is not useful with rod vision testing) object

(approximately 10 mm in diameter) is moved along the perimeter from the

outside in and the peripheral field is mapped out in degrees. The outside

limits represent where the patient, while fixing on a central target, first sees

the moving object. A simple and more practical technique is used at the

bedside. The patient is asked to fixate on the examiner's pupil as in testing

central vision, and a large object, frequently the examiner's index finger, tip

first, is moved into the patient's visual field (confrontation) from a position

lateral to the patient's head. This is a rapid and easy way to approximate

peripheral visual fields (Fig. 3-10).

Double simultaneous stimulation

It is useful at the bedside to use tachistoscopic double simultaneous

stimulation (TDSS) of the visual fields. This entails the rapid momentary

presentation of two objects simultaneously into opposite visual fields. In

practice, a momentary movement of the tip of the index finger in both fields

is suitable (see Fig. 3-10). TDSS testing is advantageous because minor

partial field deficits, which may not be picked up on unilateral stimulation

become apparent; the object in the abnormal field is extinguished. A rapid

single excursion of the examiner's index fingers in the peripheral fields is

adequate (see Fig. 3-10). Extinction in the visual field may represent either a

partial dysfunction in the visual pathways or may be due to inattention

phenomenon to one side of the body. This latter difficulty is usually part of a

broader syndrome of hemispatial inattention (neglect), usually resulting

from contralateral parietal (and occasionally frontal) association cortices.

References

Brodal, A.: Neurological Anatomy in Relation to Clinical Medicine, ed.

2. New York, Oxford University Press, 1969.

Cogan, D.G.: Neurology of the Ocular Muscles, ed. 2. Springfield, IL,

Charles C. Thomas, Publisher, 1956.

Monrad-Krohn, G.H., Refsum, S.: The Clinical Examination of the

Nervous System, ed. 12. London, H.K. Lewis & Co., 1964.

Spillane, J.D.: The Atlas of Clinical Neurology, ed. 2. New York, Oxford

University Press, 1975.

Walsh, F.B, Hoyt, W.F.: Clinical Neuro-ophthalmology, ed. 3.

Baltimore, Williams & Wilkins Co., 1969.

Questions

Define the following terms:

anosmia, homonomous, hemianopsia, quadrantanopsia, scotoma,

papilledema, papillitis, optic neuritis.

Anosmia is a loss of the sense of smell (this can be unilateral or bilateral).

Homonomous is a term referring to overlapping areas of the visual field of each eye.

Hemianopsia (or hemianopia) is a loss of visual perception of one-half of the visual world.

Quadrantanopsia is a loss of visual perception of one-quarter of the visual world.

Scotoma is a patch of vision loss.

Papilledema is swelling of the optic nerve head usually produced by congestion of the

central retinal veins. This usually happens due to increased intracranial pressure.

Papillitis is swelling of the optic nerve head due to inflammation.

Optic neuritis is inflammation of the optic nerve.

3-1. How do you test olfaction?

Answer 3-1. Olfactory nerve is tested with aromatic compounds presented to each nostril.

3-2. What is the most common cause of unilateral anosmia?

Answer 3-2. Most common cause of unilateral anosmia is blockage of nasal passage.

3-3. In whom is it particularly important to test olfaction?

Answer 3-3. Olfactory testing is most important in patients with head injury, mental status

change and seizure.

3-4. How can you determine if visual acuity problems are due to refractive or

to nerve problems?

Answer 3-4. Visual acuity problems that are refractive improve with pinhole testing

(retinal or optic nerve problems do not).

3-5. What is the significance of finding a monocular visual loss?

Answer 3-5. Assuming that this is not due to refractive problems in the eyeball (usually

ruled out by a funduscopic examination) monocular problems are anterior to the optic

chiasm (retina or optic nerves).

3-6. What is the significance of finding a homonomous visual field deficit?

Answer 3-6. Homonymous visual field problems are posterior to the optic chiasm.

3-7. Where would a lesion that produced bitemporal hemianopsia be

located?

Answer 3-7. Bitemporal hemianposia is often due to problems at the optic chiasm (such

as with pituitary tumors).

3-8. How can lesions of the parietal or temporal lobes produce vision loss?

What kind of loss would you expect to find?

Answer 3-8. Optic radiations that pass from the thalamus to the visual cortex in the

occipital lobe either pass through the parietal lobe (lower visual field) or temporal lobe

(Meyer's loop - upper visual field) - may produce quadrananopsia of either the

contralateral lower visual world (parietal lobe) or upper visual world (temporal lobe).

3-9. Where on the visual cortex is the representation of the center of vision?

Answer 3-9. The center of vision is represented near the occipital pole (often supplied by

middle cerebral artery).

3-10. What artery supplies the visual cortex?

Answer 3-10. Most of the visual cortex is supplied by posterior cerebral arteries.

3-11. How can you distinguish papilledema from papillitis?

Chapter 4 - Extraocular movement

Eye movements are controlled by muscles innervated by cranial nerves III,

IV and VI. In this chapter, the testing of these cranial nerves will be

discussed. The most common symptom of damage to these nerves is double

vision. The oculomotor nerve has the additional function of control of the

pupil and therefore this will be discussed here as well. Eye movements are

carefully controlled by other systems. Some of these will be discussed here,

while others, such as the vestibular system, will primarily be discussed in

other chapters.

Cranial nerves III, IV, VI. Ocular Motility

Oculomotor function can be divided into two categories: (1) extraocular

muscle function and (2) intrinsic ocular muscles (controlling the lens and

pupil). The extraocular muscles include: the medial, inferior, and superior

recti, the inferior oblique, and levator palpebrae muscles, all innervated by

the oculomotor nerve (III); the superior oblique muscle, innervated by the

trochlear nerve (IV); and the lateral rectus muscle, innervated by the

abducens nerve (VI). The intrinsic eye muscles are innervated by the

autonomic systems and include the iris sphincter and the ciliary muscle

(innervated by the parasympathetic component of cranial nerve III), and the

radial pupillodilator muscles (innervated by the ascending cervical

sympathetic system with its long course from spinal segments T1 through

T3).

Extraocular muscle function

The muscles of the eye are designed to stabilize and move the eyes. All eye

muscles have a resting muscle tone that is designed to stabilize eye position.

During movements, certain muscles increase their activity while others

decrease it. The movements of the eye include: adduction (the pupil

directing toward the nose); abduction (the pupil directed laterally); elevation

(the pupil directed up); depression (the pupil directed down; intorsion (the

top of the eye moving toward the nose); and extorsion (the superior aspect

of the eye moving away from the nose). Horizontal eye movements are

rather simple. Increased activity of the lateral rectus will direct the pupil

laterally, while increased activity of the medial rectus will direct it medially.

However, movements of the eyes above or below the horizontal plane are

complicated and require, at the minimum, activation of pairs of muscles.

This is because the obit is not directed straight forward in the head and,

therefore, there is no one muscle positioned to direct the eye straight up or

down without the simultaneous occurence of unwanted movements. Because

of this, the protocol for testing eye movements is somewhat more

complicated than might be expected.

Figure 4-1 illustrates the correct eye positions for testing the

extraocular muscles in relative isolation. As can be seen in Figures 4-1 and

4-2, a lateral position of the eyeball is necessary for testing the inferior and

superior recti, whereas a medial position is necessary for testing the inferior

and superior oblique. This is because, in the position of lateral gaze, the

superior and inferior rectus muscles are in line with the axis of the globe,

"straightening out the pull" of these muscles and allowing them to move the

eye straight up or down. When the eye is directed nasally (medially), the

oblique muscles align with the axis of the globe and are, therefore, the

prime muscles for vertical gaze when the eye is adducted. Vertical gaze from

the neutral position (Fig. 4-1) is accomplished by simultaneous activation of

the superior rectus and inferior oblique (for upgaze) and of the inferior

rectus and superior oblique (for downgaze). It is not necessary to have the

patient look straight up and down in order to test each of the extraocular

muscles. However, this may reveal evidence of vertical nystagmus (a sign of

brain stem vestibular damage) and to determine the integrity of the

midbrain center for vertical gaze (which may be defective despite adequate

individual muscle activity). illustrates the expected findings with isolated

loss of function of cranial nerves III, IV, and VI.

Since there is resting tone in all of the eye muscles, isolated weakness

in one muscle results in deviation of the eye due to the unopposed action of

all of the remaining muscles. This typically results in double vision when the

person tries to look straight ahead (although some patient may ignore the

input from one eye). The afflicted person often adjusts their head position in

an attempt to ameliorate the double vision caused by the muscle imbalance.

The position that their head assumes is one that permits them to use their

"good eye" to line up with the affected one. This is often successful in cases

of isolated damage to cranial nerve IV or VI, with the head assuming the

position shown in Figure 4-3. In this figure, the dashed vector lines show

which directions of muscle pull are lost. The solid vector lines indicate the

resting tonus of the remaining extraocular muscles. Note that the head is

tilted in CN IV damage. This is the classic position from which the English

phrase "cockeyed" is derived. When cranial nerve III is involved, there may

be enough ptosis to close the eye (preventing diplopia). However, if the eye

is open, there is usually too much imbalance to overcome by head

positioning and patients usually have diplopia.

The person with an extraocular muscle defect of recent onset usually

complains of double vision (diplopia). This results from the inability to fuse

the images on the macular regions (central vision) of both eyes. Since the

weak muscle is unable to bring the eye to a position in which the object is

focused on the macula, the image falls on a more peripheral part of the

retina. The person sees the object in the field appropriate to the new retinal

position (i.e., always farther toward the periphery in the direction of

attempted gaze. Additionally, because the image falls on retinal region with

fewer cones, it is less distinct. The patient may compare it to the "ghost

images" seen on maladjusted television sets.

Sometimes it is very obvious which eye is not moving sufficiently when

you perform the "6 positions of gaze". Also, the direction of the diplopia can

give clues about weakness. For example, horizontal diplopia (where the

images are separated horizontally) is due to problems with the medial and

lateral recti, while vertical diplopia is due to problems with one or more of

the other muscles. When it is not obvious on observation, one can delineate

which extraocular muscle or muscles are defective by determining which

eye sees the abnormal image (i.e., the blurry image that is farthest toward

the periphery in direction of eye movement). This can be done by placing a

transparent red piece of plastic or glass in front of one eye and asking the

patient (who is observing a small light source such as a penlight or white

object) which image is red, the inside or outside, lower or upper, depending

on whether the diplopia is maximum in the vertical or lateral field of gaze.

Figure 4-4 demonstrates the findings in one patient with medial rectus

dysfunction and in one with lateral rectus dysfunction. The abnormal image

in both cases is laterally displaced in the field of gaze and blurred (even

though different eyes are involved in each case). Alternatively, if a red glass

is not available, you can use the cover test to determine which eye is

involved. In this case you will need to ask the patient to identify which image

disappears when you cover one eye. Again, the eye that is projecting the

image most off to the periphery is the one that is affected. The red glass and

cover tests are particularly useful in delineating minimal muscle

dysfunction, in which it is frequently difficult to determine which muscles

are involved by observation on primary muscle testing.

Central control of eye movement

It is worthwhile at this point to review the anatomy of the central pathways

of the oculomotor system. Figures 4-5 and 4-6 schematically outline the

major central pathways that are important to conjugate lateral gaze,

conjugate vertical gaze and convergence. Additionally, the deficits caused by

destructive lesions in various parts of these systems are diagrammed.

The central control of eye movement can be distilled into the principle

types of functions. These include voluntary, conjugate horizontal gaze

(looking side-to-side); voluntary, conjugate vertical gaze (looking up and

down); smoothly tracking objects; convergence; and eye movements

resulting from head movements. These latter movements, are part of the

vestibular reflexes for eye stabilization and will be discussed with the

vestibular nerve. The vestibular chapter is also where nystagmus (a to-and-

fro movement of the eye) will be discussed.

The movements of they eyes produce by the central nervous system are

conjugate (i.e., both eyes moving in the same direction in order to keep the

eyes focused on a target) except for convergence, which adducts the eyes to

focus on near objects. Voluntary horizontal gaze in one direction begins with

the contralateral frontal eye fields (located in the premotor cortex of the

frontal lobe). This region has upper motor neurons that project to the

contralateral paramedian pontine reticular formation (PPRF), which is the

organizing center for lateral gaze in the brain stem. The PPRF projects to

the ipsilateral abducens nucleus (causing eye abduction on that side). There

are fibers extending from the abducens nucleus, which is located in the

caudal pons, to the contralateral oculomotor nucleus of the midbrain. The

projection pathway is the medial longitudinal fasciculus (MLF). The

oculomotor nucleus then activates the medial rectus, adducting the eye in

order to follow the abducting eye. This is illustrated schematically in figure

4-9 for voluntary horizontal gaze to the left.

Damage to the frontal eye-fields will initially prevent voluntary gaze

away from the injured frontal lobe. However, that improves with time.

Damage to the PPRF will abolish the ability to look toward the side of the

lesion. Damage to the MLF produces the curious finding of “internuclear

ophthalmoplegia” in which the patient will be able to abduct the eye, but the

adducting eye will not follow. Additionally, there will be some nystagmus in

the abducting eye.

Vertical gaze (Fig. 4-10) does not have one center in the cerebral cortex.

Diffuse degeneration of the cortex (such as with dementia) can diminish the

ability to move the eyes vertically (particularly upward). There is a brain

stem center for vertical gaze (in the midbrain – the rostral interstitial

nucleus [of Cajal]). Degeneration of this nucleus (such as can occur in rare

conditions like progressive supranuclear palsy) can abolish the ability to

look up or down. Additionally, there are connections between the two sides

that traverse the posterior commissure. Pressure on the dorsum of the

midbrain, such as by a pineal tumor, can interrupt these fibers and prevent

upgaze (Parinaud syndrome).

Smooth tracking eye movements are mediated through a more

circuitous pathway that includes the visual association areas (necessary in

order to fix interest on a visual target) and the cerebellum. Cerebellar

damage often produces jerky, uncoordinated movements of the eyes.

Pupillary function

The iris receives both sympathetic and parasympathetic innervation: (1) the

sympathetic nerves innervate the pupillary dilator muscles; and (2) the

parasympathetic nerve fibers (from CN III) innervate the pupillary

constrictor (sphincter) muscles as well as the ciliary apparatus for lens

accommodation. Figures 4-7 and 4-8 show the origins and courses of these

two systems.

During the normal waking state the sympathetics and parasympathetics

are tonically active. They also mediate reflexes depending in part on

emotionality and ambient lighting. Darkness increases sympathetic tone and

produces pupillodilation. Increased light produces increased

parasympathetic tone and therefore pupilloconstriction (this also

accompanies accommodation for near vision). During sleep, sympathetic

tone is depressed and the pupils are small. Normal waking pupil size with

average ambient illumination is 2 to 6 mm. With age, the average size of the

pupil decreases. Approximately 25% of individuals have asymmetric pupils

(anisocoria), with a difference of usually less than 0.5 mm in diameter. This

must be kept in mind when attributing asymmetry to disease, particularly if

there are no other signs of neurologic dysfunction.

At the bedside, the first step in evaluating pupil dysfunction is

observation of the resting size and shape. A small pupil suggests

sympathetic dysfunction; a large pupil, parasympathetic dysfunction. Loss of

both systems would leave one with a nonreactive, midposition pupil, 4-7 mm

in diameter, with the size varying from individual to individual. This is seen

most often in persons with lesions that destroy the midbrain (see Chap. 24).

Pupillary reflexes

Next, the integrity of the papillary reflex section is evaluated.

Parasympathetic function is tested by having the patient accommodate, first

looking at a distant object, which tends to dilate the pupils and then quickly

looking at a near object, which should cause the pupils to constrict.

Additionally, the pupils constrict when the patient is asked to converge,

which is most easily done by having them look at their nose. There are rare

conditions damaging the pretectal region that differentially affect the

constriction produced by convergence from that produced by accomodation.

More common is the loss of the light reflex with preservation of

accommodation and convergence pupilloconstriction (this has been termed

the Argyll-Robertson pupil). This may be caused by lesions in the peripheral

autonomic nervous system or lesions in the pretectal regions of the

midbrain. Variable amounts of sympathetic involvement are usually present,

leaving the pupil small in the resting state. Although this was commonly

associated with tertiary syphilis in the past, the Argyll-Robertson pupil is

seen most often associated with the autonomic neuropathy of diabetes

mellitus.

The light reflex is tested by illuminating first one eye and then the other.

Both the direct reaction (constriction in the illuminated eye) and the

consensual reaction (constriction in the opposite eye) should be observed.

The direct and consensual responses are equal in intensity because of equal

bilateral input to the pretectal region and Edinger-Westphal nuclei from

each retina (see Fig. 4-7).

Pupillodilation, which can be tested by darkening the room or simply

shading the eye, occurs due to activation of the sympathetic nervous system,

with associated parasympathetic inhibition. A sudden noxious stimulus, such

as a pinch (particularly to the neck or upper thorax), causes active bilateral

pupillodilation. This is called the cilio-spinal reflex and depends

predominantly on the integrity of the sensory nerve fibers from the area, the

upper thoracic sympathetic motor neurons (T1- T3 lateral horn) and the

ascending cervical sympathetic chain (see Fig. 4-8). Interruption of the

descending sympathetic pathways in the brain stem frequently has no effect

on the reflex. Therefore, if the patient has a constricted pupil presumably

secondary to loss of sympathetic tone, absence of the ciliospinal reflex

suggests peripheral sympathetic denervation or, if other neurologic signs

are present, damage to the upper thoracic spinal cord. Presence of the reflex

despite depressed resting sympathetic tone suggests damage to the

descending central sympathetic pathways.

Horner's syndrome is a constellation of signs caused by lesions in the

sympathetic system. Sweating is depressed in the face on the side of the

denervation, the upper eyelid becomes slightly ptotic and the lower lid is

slightly elevated due to denervation of Muller's muscles (the smooth muscles

that cause a small amount of lid-opening tone during alertness). Vasodilation

is transiently seen over the ipsilateral face, and the face may be flushed and

warm. These abnormalities, in addition to pupilloconstriction, are seen in

conjunction with peripheral cervical sympathetic system damage.

The final neuron in the cervicocranial sympathetic pathway arises in the

superior cervical ganglion and sends its axons to the head as plexuses

surrounding the internal and external carotid arteries. Lesions involving the

internal carotid artery plexus (as in the middle-ear region) cause miosis (a

small pupil) and ptosis and loss of sweating only in the forehead region - the

area of the face supplied by the internal carotid system. Lesions of the

superior cervical ganglion cause the same problems, except that loss of

sweating occurs over the whole side of the face. Destruction of the external

carotid plexus causes sweating loss over the face that spares the forehead,

without pupillary or eyelid changes. Lesions of the lower portion of the

cervical sympathetic chain (e.g., carcinoma of thyroid) cause a Horner's

syndrome with loss of sweating in the face and neck, and if the lesion is at

the thoracic outlet (such as tumors of the apex of the lung), loss of sweating

extends to the upper extremity. Lesions of the brainstem and cervical spinal

cord descending sympathetic pathways cause a Horner's syndrome with

depression of sweating over the whole side of the body. Lesions of the spinal

cord below T1- T3 cause a loss of sweating below the level of the lesion but

no Horner's syndrome. Testing for sweating defects can therefore be very

useful in localization of the lesion. A simple, but messy way to test sweating

is to warm the patient and watch for asymmetrical loss of sweating using

starch and iodine. The parts to be tested are painted with an iodine

preparation (e.g., forehead, cheek, neck, hand and foot) and then when they

are dry, the areas are dusted with starch. When the patient sweats after

being warmed with blankets (covering the tested areas with plastic is

useful), the iodine runs into the starch and blackens it. Asymmetries are

relatively easy to observe.

Amblyopia

Before concluding this discussion of eye movements it would be appropriate

to say a few words about "amblyopia" (literally, "dim eye"). This is a

condition in which one eye obviously drifts off target (some have called it a

"wandering eye"). However, the patient is unaware of this and does not see

double.

This is most serious in children and occurs for one of two reasons. First

of all, it may occur due to severe muscle weakness or scarring. In this case

the child cannot keep the two eyes fixed on the same target. The other cause

is poor vision (usually in one eye). The reason that there is no double vision

is that the brain "turns off" input from the bad eye. The reason this is so bad

in young children is that, up until late childhood, functionally "turned off"

synapses will actually loose their connections with neurons at the level of

the visual cortex. These synapses will be replaced by synapses of fibers from

the intact eye and the patient will become permanently blind in that eye.

"Turning off" an eye for one continuous month for each year of life (i.e., for 5

straight months in a 5-year old) is enough to cause permanent blindness.

This does not happen in adolescence or adulthood because synapses have

stabilized. Interestingly, the pupillary light reflex is unaffected since the

projections from the retina to the pretectum are intact.

The treatment is to force the patient to use the eye at least part of the

day (while providing as much visual correction as possible for the affected

eye). This is often done by patching the "good eye" during school time (in a

more controlled environment).

References

Brodal, A.: Neurological Anatomy in Relation to Clinical Medicine, ed.

2. New York, Oxford University Press, 1969.

Cogan, D.G.: Neurology of the Ocular Muscles, ed. 2. Springfield, IL,

Charles C. Thomas, Publisher, 1956.

Monrad-Krohn, G.H., Refsum, S.: The Clinical Examination of the

Nervous System, ed. 12. London, H.K. Lewis & Co., 1964.

Spillane, J.D.: The Atlas of Clinical Neurology, ed. 2. New York, Oxford

University Press, 1975.

Walsh, F.B, Hoyt, W.F.: Clinical Neuro-ophthalmology, ed. 3.

Baltimore, Williams & Wilkins Co., 1969.

Questions

Define the following terms:

strabismus, abduction, adduction, elevation, depression, convergence,

accomodation, diplopia, meiosis, mydriasis, myopia, hyperopia,

conjugate, consensual, extraocular, amblyopia, ptosis, anisocorea.

Strabismus is a position of the eyes where they are not directed at the same target (in

some parts of the country this is termed a "squint").

Abduction is bringing the pupil away from the nose.

Adduction is bringing the pupil toward the nose.

Elevation is moving the pupil above the horizon.

Depression is moving the pupil below the horizon.

Convergence is directing both eyes toward the nose.

Accomodation is a combination of convergence, pupil constriction and change in lens

shape to permit focus on a near object.

Diplopia is double vision. This can be horizontal, vertical or skew.

Meiosis is constriction of the pupil.

Mydriasis is dialation of the pupil.

Myopia is an inability to see at distance ("nearsighted") with light focusing in front of the

retina.

Hyperopia is an inability to see close up ("farsighted") with light behind the retina.

Conjugate - "together". That is, the eyes moving in parallel to keep images focused on the

same part of each retina (preventing diplopia).

Consensual means "happening on both sides at the same time". A consensual reflex is

one where the response is bilateral when the stimulus is unilateral (such as the papillary

light reflex).

Extraocular means outside the eye and specifically is used to describe the muscles that

attach to the outside of the eyeball and move it.

Amblyopia literally means "dim eye". This is a drifting or "lazy" eye that usually happens

because one eye has bad vision. The brain often "turns off" control of that eye and the

eye drifts. The patient usually does not have diplopia because input from that eye is

turned off. In one of the most remarkable illustrations of plasticity, the eye can become

permanently blind in children if this is not treated.

Ptosis is a drooping of the upper eyelid.

Anisocorea is an inequality of pupil size. This is usually not clinically significant unless it

reaches one millimeter in difference.

4-1. Which muscles would be active in the right and left eye when looking up

and to the right?

Answer 4-1. In the right eye the lateral rectus and the superior rectus would be the prime

movers, while in the left eye, the medial rectus and the inferior oblique would be most

active.

4-2. Which muscles would be active in the right and left eye when looking

down and to the left?

Answer 4-2. In the right eye the medial rectus and the superior oblique would be the

prime movers, while in the left eye, the lateral rectus and the inferior rectus would be

most active.

4-3. What position will the patient's head assume (in order to prevent

diplopia) if their right trochlear nerve is damaged?

Answer 4-3. Head tilted to the left and chin turned slightly to the right ("cockeyed").

4-4. When a patient has double vision, in which position will they have the

furthest separation of the images?

Answer 4-4. The images will be furthest apart when the eyes look in the direction that the

weak muscle is most active.

4-5. What is the significance of horizontal diplopia (where the images are

side-by-side) as opposed to vertical diplopia?

Answer 4-5. Horizontal diplopia results from weakness of the lateral or medial rectus

muscles; vertical diplopia is due to weakness of one of the other muscles.

4-6. Which eye (the one that is moving normally or the weak one) will see

the image that is furthest displaced from the center of vision?

Answer 4-6. The "bad eye" sees the image that is furthest toward the periphery of vision.

4-7. Where is the cortical center that controls lateral gaze? Where is the

lateral gaze center in the brain stem?

Answer 4-7. Lateral gaze centers include the frontal eye fields in the frontal lobes of the

cerebral cortex and the paramedian pontine reticular formation.

4-8. Is there a vertical gaze center in the cerebral cortex? Is there a brain

stem vertical gaze center?

Answer 4-8. Vertical gaze is a diffuse cerebral cortical phenomenon, while there is a

vertical gaze center in the rostral midbrain (the rostral interstitial nucleus).

4-9. What are the potential causes of ptosis?

Answer 4-9. Ptosis may be due to weakness of the levator palpebrae muscle (or CNIII

damage) or due to damage to the sympathetics (due to weakness of the small, superior

tarsal muscle).

4-10. What are the components of Horner's syndrome?

Answer 4-10. Horner's syndrome (ptosis, meiosis, anhidrosis and possibly flushing) is from

damage to sympathetics anywhere along their course.

4-11. What are the functions of sympathetic and parasympathetic nerves to

the orbit?

Answer 4-11. Sympathetics dilate the pupil, parasympathetics (CN III) constrict the pupil

to light and accommodation; there is balance between sympathetics and

parasympathetics.

4-12. Where is the brain stem center for the pupillary light reflex?

Chapter 5: Facial sensations & movements

In this chapter, the functions of the trigeminal (CN V) and facial (CN VII)

nerves will be discussed. Symptoms of damage to the trigeminal system are

mainly loss of sensation in the face, although the mandibular division of the

trigeminal nerve also controls jaw motion. Damage to the facial nerve mainly

manifests as weakness of muscles of facial expression, although it may also

affect taste sensation in the anterior part of the tongue. It is critical to

distinguish damage of the facial nerve from damage to the connections from

the cerebral cortex to the brain stem, which selectively weakens muscles of

the lower portion of the face, contralateral to the side of damage.

V. Trigeminal Nerve

The three divisions of the fifth nerve (I. Ophthalmic, II. Maxillary, and III.

Mandibular) are the source for somatic sensation over the entire face (Figs.

5-1 and 5-2), the eye, the nasal passages and the oral cavity.

Facial sensations

Facial sensation can be tested simply at the bedside by having the patient

close their eyes and respond affirmatively to touch with a light wisp of

cotton over the three divisions of the trigeminal nerve. The patient should be

asked to compare the perception on the two sides. Pain perception as tested

by a pin can be similarly checked, although temperature sensation (which is

mediated by the same pathways, can replace the use of a pin. Sensory

testing is, by nature, subjective (i.e., the examiner depends on the reliability

of the subject). It is important to define the pattern and distribution of

sensory alteration since that can go a long way to both localizing the lesion

and also validating the sensory findings. The patient with hysterical or

feigned sensory loss in the face frequently has bizarre perceptive patterns

such as a hairline or perfect midline demarcation of hyposensitivity. Neither

pattern can be explained on the basis of the central or peripheral

distribution of the trigeminal system (see Fig. 5-1). Additionally, the inability

to detect the vibrations of a tuning fork placed on one side of the head

(when the other side can detect it) is not physiological since the entire head

vibrates. The subjective tests of facial sensation can be objectified by

examining certain reflex responses such as the corneal reflex (where the eye

briskly closes in response to a wisp of cotton touching the cornea).

Asymmetries of this are a good sign of sensory impairment at least in the

distribution of the ophthalmic division of the trigeminal nerve (see below).

Jaw movements

The temporalis, masseter, and pterygoid muscles (muscles of mastication)

are supplied by the motor division of the mandibular branch of cranial nerve

V and subserve jaw movement. Supranuclear innervation of these muscles

(hemispheric and brainstem pyramidal and extrapyramidal systems) is

essentially symmetrically bilateral. A unilateral lesion above the level of the

fifth-nerve motor nucleus, therefore, does not cause any obvious weakness

of jaw motion. Large bilateral lesions of the hemisphere or brain stem

(above the fifth-nerve nucleus) can cause bilateral weakness of voluntary jaw

movement. If the bilateral involvement lies above the brain stem, very basic

brain stem-mediated chewing reflexes may remain and actually become

hyperactive. The jaw jerk reflex is a muscle stretch reflex in which both the

sensory and motor nerve fibers are contained in the trigeminal nerve. This is

elicited by lightly tapping the relaxed open jaw in a downward direction.

This would be lost after trigeminal nerve damage and hyperactive with

injury above the pons (see Chap. 10).

The paired temporalis and masseter muscles function in jaw closure,

and the medial pterygoid muscle closes the jaw and moves it from side-to-

side (grinding motion). The lateral pterygoid muscles (along with some of

the upper neck muscles) open the jaw in concert with a downward and

opposing inward motion (Fig. 5-3). When one lateral pterygoid is weak, the

jaw deviates toward the weak side on opening, with the inward vector of the

opposite pterygoid being unopposed (Fig. 5-4).

Observation of temporal region for atrophy and palpation of the

symmetry of muscle bulk and tension during tight jaw closure test the

innervation of the temporalis and masseter muscles.

Corneal reflex

The corneal reflex is mediated by sensory fibers in the trigeminal nerve and

motor fibers in the facial nerve. It consists of a bilateral blink response when

the edge of the cornea is touched from the side with a wisp of cotton. The

examiner should approach from the extreme corner of the eye in order to

avoid a visually evoked blink response. It is a useful and objective test for

evaluating simultaneously the ophthalmic division of the fifth-nerve (the

afferent limb) and the seventh-nerve motor innervation of the orbicularis

oculi (the efferent limb). Both the eye that is touched and the opposite eye

are observed since they should both close equally and consensually (a

consensual reflex is one in which the motor response is bilateral to a

unilateral stimulus. The corneal reflex is a sensitive and objective indicator

of fifth- and seventh-nerve dysfunction. A good example of dysfunction

occurs with eight-nerve tumors (acoustic neuromas), which comprise

approximately 5% of all intracranial tumors in adults (see Fig. 5-2). Patients

may present with unilateral hearing loss, and on routine neurologic

evaluation the only other indication of involvement may be depression of the

ipsilateral direct and contralateral consensual corneal reflex. This results

from pressure by the tumor, which lies in the angle between the cerebellum

and pons, on the superficially positioned descending tract and nucleus of the

trigeminal nerve (which mediates pain and temperature sense from the

face). If the depression of the reflex were secondary to seventh-nerve

hypofunction, only the direct response would be depressed; the contralateral

consensual response would be full because the sensory limb of the reflex,

mediated by the trigeminal nerve, would be intact.

Trigeminal neuralgia

An instructive example of trigeminal nerve dysfunction is trigeminal

neuralgia (tic douloureux), an irritation of the nerve that probably occurs

due to contact with anomalous intracranial blood vessels. This process

causes severe paroxysms of pain in one or more divisions of the trigeminal

nerve, with the maxillary division being most often affected and the

ophthalmic least. In the past, surgeons attempted to cut the various

peripheral branches of the trigeminal root. However, this would result in

"numbness" and pain would usually return some months later. At one time,

complete damage to the root became a popular form of permanent cure. A

great difficulty with both of these procedures is that the area of anesthesia

can become spontaneously painful (denervation hypersensitivity, a form of

neuropathic pain). Also, the eye and face can be damaged because of the

loss of sensitivity. These destructive surgical procedures have fallen out of

favor.

Fortunately, various medications (mostly in the family of

anticonvulsants) suppress the excess excitability in the trigeminal neurons

and are successful in relieving tic in many persons for long periods of time.

Nonetheless, there are patients who do not get adequate response to

medications and several other interventions can be successful in relieving

these medically refractory patients. Glycerol, injected into the region around

the trigeminal ganglion, often produces relief that extends for years after

the procedure (it is thought to produce some selective nerve damage). A

radiofrequency probe can be placed into the trigeminal ganglion

(percutaneously, through the foramen ovale) and selective lesions can be

made to the nerve fibers from the painful region of the face. The most

elegant surgical treatment (but most invasive) involves approaching the

trigeminal nerve from an occipital craniotomy and placing some Teflon

between any irritating arteries and the trigeminal nerve root. This often

results in permanent relief of the symptoms.

VII. Facial Nerve

Most of the facial nerve is comprised of motor innervation of the muscles of

facial expression. In addition, it subserves several other functions including:

taste perception from the anterior two-thirds of the tongue; perception of

cutaneous stimuli in the external auditory canal and over part of the pinna

and mastoid region; innervation of the stapedius muscle in the middle ear;

and innervation of the lacrimal gland and two of the salivary glands (the

submaxillary and submandibular).

Many of these functions are difficult to test and more difficult to

quantify (such as salivation and lacrimation (Fig. 5-5). However, some of

these functions can be tested and give clues as to the location of facial nerve

damage.

Taste in the anterior tongue is tested with application of a thick sugar

solution on a Q-tip to the protruded tongue. Care must be taken to prevent

this from spreading to the other side and the mouth must be rinsed out

thoroughly between trials. The chorda tympani (the branch mediating this

sensation) leaves the parent nerve, crossing through the middle ear (where

it can also be damaged by severe infections, etc).

Loss of function of the stapedius muscle may reflect as "hyperacusis",

i.e., perception of sound as excessively loud an irritating on the side of

damage. This branch also arises at the level of the middle ear.

Facial expression

The great majority of facial nerve fibers are involved in producing facial

expressions. Careful observation of the patient's face during conversation

and at rest almost always reveals facial weakness. Additionally, the face may

"droop" on the side of damage due to the effects of gravity. The nerve can be

further tested by: having the patient close their eyes and lips tightly (the

force of closure can be felt by manually trying to open them); having the

patient grimace (show their teeth); having the patient look up (elevating the

eyebrows and creasing the forehead); and also having the patient fill their

cheeks with air with their lips tightly pursed. If one or both sides of the face

are weak, s/he will have difficulty holding the air in. Tapping each cheek

accentuates the difficulty on the appropriate side.

The most common cause of facial weakness is Bell's palsy, an idiopathic

condition that may result from viral infection-induced inflammatory swelling

of the facial nerve in its canal. Since the canal is very long and tight,

swelling can put pressure on the nerve, resulting in damage either by direct

effects or by impairing blood flow in the nerve. In some cases, facial palsy is

produced by a very clear viral infection with Herpes Zoster, often associated

with ear pain and vesicles on the tympanic membrane. Lyme disease also

has a proclivity to produce facial palsy, sometimes bilateral. The hallmark of

peripheral facial palsy is that it involves the entire side of the face, including

weakness of the forehead muscles as well as those around the eye and

mouth. This is because fibers to all of these regions of the face are packed

together in the facial canal. Most cases of uncomplicated Bell's palsy recover

quite well. In its most severe form, infarction of the nerve may occur with a

prolonged and not infrequently incomplete process of regeneration. This is

more common when a longer course of the nerve is affected, accompanied

by ageusia (loss of taste) and hyperacusis.

The facial nerve begins at the facial motor nucleus of the caudal pons. It

is not common to damage this nucleus and due to the proximity of many

sensory and motor pathways running through the brain stem, there are

almost always other signs of neurologic damage (hemiparesis,

hemihypesthesia, gaze palsy, etc) when the facial nerve is affected here.

It should be obvious that face movement is under voluntary control.

However, it is also under control of the limbic system, where strong

emotions can be seen in face involuntarily. Accordingly, there is more than

one pathway for "supranuclear" control of the face and these pathways can

be damaged independently. Corticobulbar (pyramidal) projections from the

motor cortex (precentral gyrus) through the genu of the internal capsule are

the major substrate for voluntary facial movement (Fig. 5-6). The cerebral

cortical projections to the facial motor neurons innervating the upper face

are essentially bilateral (i.e., each cortical hemisphere provides innervation

to both sides). Therefore, unilateral lesions (such as a stroke affecting one

hemisphere or the internal capsule) will not produce weakness of the upper

face muscles. On the other hand, facial motor neurons that innervate the

muscles of the lower face receive input largely from the contralateral

hemisphere (i.e., the right hemisphere activates motor neurons of the left

facial nucleus, and vice-versa). Therefore, a lesion involving the right motor

cortex (e.g., carotid-middle cerebral arterial system occlusion and

hemispheric infarction) causes a weakness of voluntary left lower facial

movement that is especially noticeable while the patient is talking,

grimacing (usually elicited by asking the patient to bare their teeth or

gums), or resting. In the latter instance, the corner of the mouth droops and

there may be some widening of the palpebral fissure (eye) (Fig. 5-7). On the

other hand, the forehead is normally creased when a person raises their

eyebrows or looks toward the ceiling. This distinguishes the "supranuclear"

weakness of the face from the weakness of the whole side of the face, due to

damage of the peripheral facial nerve, as seen with Bell's palsy.

Interestingly, despite severe weakness around the mouth with

"supranuclear facial palsy", the mouth may actually move more than normal

with emotional triggers (hypermimia, Fig. 5-7). This illustrates that limbic

motor pathways (governing postures and movements in response to strong

emotion) are distinct from the more usual motor pathways that we employ

for normal voluntary movements. When there is bilateral damage to

voluntary motor pathways, the face may be markedly overexpressive and

may not actually reflect the patient's consciously perceived emotions. This is

termed a "pseudobulbar affect".

Somatic sensation

The facial nerve has only a very small cutaneous distribution to the skin of

the external auditory canal and over the tympanic membrane, where it

overlaps with the small somatic branches of cranial nerves IX, X, and

possibly V. Additionally, nerve VII variably supplies small branches to the

ear lobe and the mastoid, which overlaps with the distributions of the

trigeminal nerve and cervical nerves 2 and 3. It is not surprising with the

considerable overlap of dermatomes that sensory testing seldom reveals

hypoesthesia when the facial nerve is damaged. However, patients with

Bell's palsy may complain of pain in the external canal and over the mastoid

region due to irritation of these nerve fibers. Herpes zoster infection may

afflict the geniculate ganglion (the sensory ganglion of the facial nerve) and

manifests itself as pain and vesicular eruption over the preceding

distribution. Facial weakness or paralysis is common with geniculate zoster

due to swelling.

References

Brodal, A.: Neurological Anatomy in Relation to Clinical Medicine, ed.

2. New York, Oxford University Press, 1969.

Cogan, D.G.: Neurology of the Ocular Muscles, ed. 2. Springfield, IL,

Charles C. Thomas, Publisher, 1956.

Monrad-Krohn, G.H., Refsum, S.: The Clinical Examination of the

Nervous System, ed. 12. London, H.K. Lewis & Co., 1964.

Spillane, J.D.: The Atlas of Clinical Neurology, ed. 2. New York, Oxford

University Press, 1975.

Walsh, F.B, Hoyt, W.F.: Clinical Neuro-ophthalmology, ed. 3.

Baltimore, Williams & Wilkins Co., 1969.

Questions

Define the following terms:

hyperacusis, agusia.

Hyperacusis is the excessive perception of sound.

Agusia is the loss of taste perception.

5-1. Which division of the trigeminal nerve has motor fibers?

Answer 5-1. Only the mandibular division of the trigeminal nerve has motor fibers (to the

muscles of mastication).

5-2. What are some good ways to distinguish hysterical sensory loss on the

face?

Answer 5-2. The trigeminal nerve does not follow artificial lines on the head (hairline,

jawline), and there is no lesion that will abolish the ability of the patient to detect a

vibrating tuning fork placed on a bony prominence of the skull. The corneal reflex may be

useful as well.

5-3. Where is the trigeminal ganglion located?

Answer 5-3. The trigeminal ganglion is lateral to the sella turcica/pituitary and in wall of

cavernous sinus.

5-4. Where does the trigeminal nerve root enter the brain?

Answer 5-4. CN V enters the pons.

5-5. What modalities would test the integrity of the spinal tract of the

trigeminal nerve?

Answer 5-5. Pin and temperature sense.

5-6. Where do pain and temperature nerve fibers in the trigeminal nerve run

after entering the pons?

Answer 5-6. Pain and temperature fibers run caudally through the lateral brain stem to

reach the spinal nucleus of V in the medulla and upper spinal cord; lateral brain stem

lesions can block ipsilateral pain from face.

5-7. What is the pathway of the corneal reflex?

Answer 5-7. The sensory llimb of the corneal reflex is the ophthalmic division of the

trigeminal nerve and the motor limb is the facial nerve. The response is consensual.

5-8. What are the symptoms of Bell's palsy?

Answer 5-8. Bell's palsy damages the facial nerve in the facial canal and weakens all

muscles of facial expression on the side of lesion. Depending on where the damage

occurs, there may be hyperacusis or loss of taste on that side of the tongue.

5-9. How can you distinguish weakness of the face that is due to damage to

the brain (such as with a stroke) from weakness due to damage of the facial

nerve?

Answer 5-9. Damage to corticobulbar fibers (from cortex to the pons) will produce

supranuclear weakness of the lower face (sparing of forehead) on the contralateral side,

while damage to the nerve should produce weakness of all muscles of facial expression

on that side.

5-10. Describe the reflex arc of the jaw-jerk reflex.

Chapter 6 - Auditory & Vestibular Function

In this chapter, the functions and clinical examination of the

vestibulocochlear nerve (CN VIII) and its central connections will be

discussed. The two distinct functions are in hearing and in control of

balance. In the case of the auditory part of CN VIII, the symptoms are

deafness or tinnitus (ringing in the ears). In the case of the vestibular part of

CN VIII, the symptoms are vertigo or imbalance, although visual disturbance

when moving may also be a complaint.

Auditory function

Testing

The vast majority of hearing problems result from peripheral disease, i.e.,

involvement of the eighth nerve or inner ear. Testing of the peripheral

system at the bedside is simple and rewarding. For screening persons who

do not complain of hearing loss, asking them to compare the sound of

rustling fingers or a ticking watch in the two ears is a useful test of acuity.

This, combined with the Weber test (see below), is adequate. To this might

be added the use a whispered voice, which represents midrange frequencies

that frequently are involved in neural deafness.

Two basic instruments can aid in testing the auditory system: a C512

tuning fork (C256 is adequate but not as sensitive; C128 is inadequate

except for testing for hyperacusis and cutaneous and bony vibratory

perception), and a mechanical watch (watch-ticking is in the 1,500 cps

range). The watch is placed next to the patient's ear and gradually moved

away. The distance at which the patient ceases to hear the tick is noted and

compared with the distance from the opposite side. If the examiner has

normal hearing, a useful comparison can be made. High-tone deafness is

measured by this test. The C512 (or C256) fork is then used to test for lower

tone falloff and, more important, to determine whether hearing loss is

caused by defects in the conduction system (conductive deafness) or by

damage to the inner ear-auditory nerve system (sensorineural deafness).

This distinction is important since different types of conditions produce

these types of deafness and the Weber test and Rinne test permit bedside

differentiation of these conditions.

More detailed clinical evaluation including special audiometric testing is

carried out in otolaryngological laboratories and can be very useful in

differentiating cochlear (inner ear) disease from direct eighth-nerve

involvement.

Weber test

Both the Weber and Rinne tests are most valuable in the patient with a

documented hearing loss (see above). These tests are particularly focused

on determining whether the loss is sensorineural or conductive. In the

Weber test, the stem of a tuning fork is placed gently against a midline

structure of the skull (i.e., the maxillary incisor teeth or vertex of the

cranium or forehead) and the patient is asked where s/he hears the sound.

Sound is transmitted to both ears through the air but particularly through

the vibrations of the bones of the skull. If sound is transmitted to both sides

equally, the sound is heard in the midline and it can be presumed that the

conduction and neural apparatus is intact. With neural deafness, the sound

transmits best to the normal side and the patient lateralizes the sound to

that side. With conduction deafness, sound transmits best to the side of the

deafness. This is thought to occur because ambient sound is prevented from

getting to the cochlea on the blocked side. This causes the nervous system

to amplify sounds on that side by sensitizing cochlear transduction. In

conductive deafness, the patient hears the tuning fork better on the affected

side because sound on the normal side is relatively depressed and

extinguished. You can demonstrate this yourself by plugging an ear with

your finger, causing conduction deafness, and then humming. The sound will

be heard better on the occluded side.

By the way, you notice the effects of ambient sound on hearing acuity

when you must talk to a friend at the top of your voice in a noisy, crowded

room and then continue talking and walk into a silent room where you find

yourselves shouting at each other.

Rinne test

In some cases the Rinne test can provide some additional information. This

tests both bone and air conduction. The examiner places the butt of a

vibrating tuning fork on the mastoid region, and when the patient ceases to

hear the vibration, the examiner places the tines close to the external

auditory meatus to check air conduction. Vibrations perceived through air

are heard twice as long as those perceived through bone, so the normal

individual reports, for example, hearing the bone vibration for 30 seconds

and then continues to hear the vibration through air for another 30-60

seconds altogether. If there is conductive deafness, bony conduction is

either normal or slightly enhanced, whereas air conduction is decreased. If

there is neural deafness, both bone conduction and air conduction are

equally suppressed. As with the watch tick, the examiner should compare

the ability of both sides to perceive the fork. A comparison of the patient's

ability to perceive the fork, as well as the watch tick, with the examiner's

ability is also useful (Schwabach test).

Pathology

Conductive deafness results from processes that occlude the sound

conduction pathways (the external auditory canal, tympanic membrane,

middle ear or the ossicles). These may be easily detected when they result

from conditions that are visible with the otoscope (blockage of the external

canal or rupture or scarring of the tympanic membrane). Some conditions of

the middle ear, such as supperative otitis media (where there is pressure in

the middle ear due to infection), or serous otitis media (where there is

obstruction of the auditory tube with a vacuum in the middle ear and

retraction of the ear drum and accumulation of some serous fluid), may be

visible, as well. Other conditions, such as otosclerosis, which results in

progressive fusion of the ossicles, may not be detectible by observation and

may require more testing.

There are many conditions that can damage the delicate hair cells of the

organ of Corti or the auditory component of CN VIII. These conditions

produce "sensorineural" hearing loss. By far, the most common cause of this

is exposure to loud noises, which typically affects high-tone hearing. Other

conditions should be considered in acute sensorineural hearing loss,

including: infectious (usually viral) or inflammatory attack on the inner ear;

ischemia (the labyrinthian artery usually arises from the anterior inferior

cerebellar artery); or trauma (especially with fracture of the skull base). A

more insidious loss of hearing can occur with Meniere syndrome. This

condition occurs due to buildup of pressure in the inner ear due to

obstructed resorption of endolymph. This pressure can cause "blowouts" of

the membranes, with attacks of sudden vertigo that improves over hours

(see the vestibular system below). It also affects hearing, with tinnitus

(usually a buzz or hum) and hearing loss (usually of low tones). The hearing

loss can be detected even in between attacks of vertigo.

While damage to the cochlear nuclei, located at the lateral aspect of the

pontomedullary junction (where CN VIII enters the brain) can cause

unilateral hearing loss, damage to other regions of the central nervous

system is unlikely to cause recognizable hearing loss. Beyond the cochlear

nuclei the auditory system makes multiple decussations in the brainstem up

to the level of the medial geniculate, and therefore auditory signals are

bilaterally distributed in the brainstem, thalamus and primary auditory

cortex (Heschl's gyri of the posterior-superior temporal lobes). Significant

loss of hearing therefore, does not occur following unilateral lesions of the

auditory system above the cochlear nuclei. Bilateral lesions may affect

hearing but are usually so devastating as to preclude clinical testing of

hearing (there are laboratory tests of hearing, described in Chap. 23, that

may help localize brain stem lesions and do not require patient cooperation).

Damage to the central nervous system occasionally impairs localization

of sound, even without affecting acuity. For example, localization difficulty

can occur with large unilateral cerebral cortical lesions. Deficits in sound

localization is most likely to occur when the primary auditory cortex is

involved but is less frequently observed with large lesions of the frontal

and/or parietal cortex. Such patients are unable, with eyes closed, to localize

an auditory stimulus with their eyes closed in the auditory field opposite the

damaged hemisphere. This can be tested at the bedside by asking the

patient to reach for a sound (such as snapping fingers) with their eyes

closed. Double simultaneous stimulation (DSS) can also be useful; the

patient may extinguish (ignore) the stimulus opposite the lesioned

hemisphere (some of this may be a neglect phenomenon, especially when

the frontal and parietal lobes are involved).

Tinnutus

Tinnitus (ringing or buzzing in the ears) is a common complaint. It is usually

due to some damage of cochlear hair cells, with spontaneous nerve activity

being produced by the damaged cells. High-pitched tinnitus is most

commonly due to damage to cells at the base of the cochlea due to excessive

sound exposure. However, it can also result from virtually any cause of inner

ear or CN VIII damage. Low pitch tinnitus (buzzing or humming) is less

common in general, but may result from excessive pressure in the inner ear

(conditions such as Meniere syndrome). Pulsatile tinnitus is most often due

to turbulence in the carotid blood flow. This can be normal but it can also

occur with carotid bruits (turbulence due to arterial narrowing). Tinnitus

that is not accompanied by hearing loss can result from medications (notably

high doses of aspirin), but often defies diagnosis. There is no cure for

tinnitus (unless a curable cause of inner ear damage is identified), although

it can occasionally be masked with other sounds.

Vestibular function

The vestibular apparatus of the inner ear is specialized to detect movement

of the head and, to a lesser extent, position in space. The vestibular portion

of CN VIII conveys these signals to the vestibular complex of the

dorsolateral brainstem at the pontomedullary junction and also to the

vestibulocerebellum (Fig. 6-1). The chief symptom of damage to the system

is vertigo, i.e., the illusion of movement. Stabilization of the eyes is a critical

function of the vestibular system. It is largely through this effect on eye

movement that we can objectively evaluate the vestibular system. The

fundamental reflex that we will discuss is the vestibulo-ocular reflex (VOR),

which moves the eyes opposite to head movement in order to stabilize

vision. Without a vestibular system, we would be unable to see anything

clearly while the head is moving. There is another reflex, the fixation reflex,

that we will discuss as well. This reflex attempts to fix the image of an object

on the retina. Between these two reflexes our vision is actually quite good

even when the head is moving (try reading a sign while nodding your head

or shaking your head "no" and you are using these reflexes, predominantly

the VOR).

We are particularly good at detecting angular acceleration (i.e.,

spinning, pitching or tumbling). If you think about it, these are the

movements that would be most important to compensate for, since they

would tend to move your eyes off of a visual target. Smooth, linear motion

would not tend to blur vision as much, nor would acceleration in a straight

line (linear acceleration). The organs of the inner ears that detect angular

acceleration are the cristae within the semicircular canals. Since the canals

are at right angles to one another in three major planes, angular

acceleration in any direction will move fluid in the particular canals that are

in the plane of movement because of flow of endolymph (actually, in normal

movements, the endolymph stays behind and the inner ear moves with the

skull). At rest, the hair cells are tonically active, releasing transmitter that

activates the peripheral end of the vestibular nerve fibers. The tonic activity

on one side is balanced by the tonic activity in the other ear and the patient

perceives that they are stable. Differential movement of fluid in one

direction in the semicircular canal increases this activity in one ear and

decreases it in the corresponding canal of the other ear, leading to a

perception of movement and reflex movement of the eyes. Most diseases of

the inner ear or vestibular nerve are destructive in nature, decreasing input

from that ear. Therefore, the tonic firing level of the opposite canal system is

no longer opposed and the patient perceives motion. Additionally, there will

be VOR-induced eye movements that result from the brain attempting to

move the eyes opposite to the direction of perceived motion. This will trigger

competing reflexes (as part of the visual fixation reflex) that will result in eye

movement in an attempt to maintain a stable image. This to-and-fro motion

is termed nystagmus.

Actually, there are two major types of nystagmus, "jerk nystagmus" and

"pendular nystagmus". The first type (and they type that is generated by the

vestibular system) is" jerk nystagmus". In this type of nystagmus, there is

relatively slow eye drift to one side produced by the VOR, with a fast

compensatory "jerk" of the eyes to reacquire the visual target. Jerk

nystagmus is named according to the direction of the fast movement, since

this is the easiest to see. This type of nystagmus can normally be seen when

an individual spins around. Here the nystagmus is initiated by the VOR

produced by head movement. Spontaneous nystagmus is produced by

vestibular damage because of the imbalance of inputs from the ears. Jerk

nystagmus can also be elicited by the visual input of objects passing by

rapidly (for example, if one stares out the side window of a moving vehicle

with posts or trees flashing past). In this case, the nystagmus is elicited by

the fixation reflex that is attempting to lock onto and track objects visually.

This type of jerk nystagmus has been termed "optokinetic" nystagmus or

"railway" nystagmus.

The other major type of nystagmus is termed "pendular" nystagmus.

This type of oscillation of the eyes does not have a fast and slow direction of

movement but rather consists of an even motion from side to side. This is

most often due to poor visual acuity (especially when young), and the

fixation reflexes that stabilize the eyes are, therefore, poorly formed. This is

more of a tremor of the eyes and does not reflect problems with the

vestibular system.

If the two inner ears are damaged symmetrically, there is little in the

way of vertigo or nystagmus. If the horizontal canals are damaged, there is

predominantly horizontal nystagmus (see Fig. 6-1), while damage to the

anterior and posterior canals will tend to produce rotary nystagmus

(clockwise or counterclockwise) due to the addition of a vertical component

to the horizontal nystagmus. Damage to the inner ear does not produce

vertical nystagmus. Rather, this suggests damage to the brain stem

vestibular apparatus.

As an illustration of what happens with unilateral vestibular damage,

let's consider the effects of sudden loss of the right labyrinthine system, for

example, as in vestibular neuronitis (a common affliction presumably viral in

origin). In this example (Fig. 6-2), the normal response of the now

unopposed opposite (left) horizontal canal system is to tonically drive the

eyes conjugately to the right. In an alert individual, there is a reflex attempt

to contain the abnormal tonic drive. This checking attempt is called the fast

component and in combination with the tonic or slow component, forms the

rhythmic to-and-fro movement - nystagmus. The tonic component

encompasses the vestibular-oculomotor brain stem systems, whereas the

fast component depends on the integrity of the cerebral hemispheres. The

right hemisphere, including cortex, basal ganglia, and diencephalon, is

responsible for the fast component to the left and the left hemisphere for the

fast component to the right, just as for voluntary and visual tracking

horizontal gaze (see Figs. 4-5 and 4-6). With loss of hemispheric function

and preservation of basic brain stem functions (e.g., in a coma from sedative

overdose), the fast component becomes weak, irregular, and finally

disappears, leaving only tonic deviation of the eyes following vestibular-

oculomotor activation. With acute unilateral hemispheric depression, such

as caused by a middle cerebral artery occlusion, the fast component to the

opposite side is depressed. The tonic component is predominant during

vestibular-oculomotor activation and drives the eyes toward the side of the

abnormal hemisphere, which is capable of little, if any, checking.

It is important to note that the brain has compensatory mechanisms for

damage to the vestibular system. Therefore, with chronic, slowly progressive

disease such as an acoustic neuroma (a tumor arising from the neurolemmal

sheaths of the eighth nerve at the internal auditory meatus), a person is

much less likely to complain of vertigo or to have significant nystagmus. This

is true also in persons following recovery from an acute destructive process

despite the lack of effective function in the destroyed system. Compensation

for even massive damage to an inner ear is quite effective. The lack of

symptoms and signs is due to central compensation and in large part,

though not entirely, depends on visual fixation. If a patient with chronic

disease or compensated acute disease closes their eyes, the examiner may

be able to detect the reappearance of the nystagmus by using and electrical

test of eye position (the electronystagmogram) or simply by feeling the

elevated corneas move through the closed lids. Vertigo usually does not

reappear, which suggests that there are means other than visual for

suppressing the illusion of movement. An excellent example of the

suppression of nystagmus and vertigo is seen in the figure skater who is

subjected to marked acceleration and deceleration of the horizontal

endolymph-cristae systems during every spin. Using visual fixation (a fix on

one object as long as possible while spinning), skaters learn to suppress

after-spin nystagmus and vertigo almost entirely. Imagine what figure

skating would like if this were not possible!

Examination

On examining a patient with suspected vestibular dysfunction,

observation for nystagmus is of primary importance prior to formal testing.

A person with, for example, acute right vestibular apparatus destructive

disease has horizontal nystagmus with the tonic component toward the

diseased right side (release of the normal left) and the fast component

toward the left (see Fig. 6-2). Usually s/he complains of vertigo (illusion of

movement of self or environment), saying that the room is spinning in the

direction of the fast component, to the left -- an illusion caused by the forced

tonic movement of the eyes and retinae. This should be called object vertigo

as opposed to subject vertigo, which is the sensation that the subject is

spinning and which occurs almost exclusively with the eyes closed. Subject

vertigo is the true vestibular illusion, unsuppressed by the retinal image.

The patient usually complains that s/he feels s/he is rotating in the direction

of the clinically observed fast component of the nystagmus.

Testing of the inner ear is not a simple matter. Asking the patient to

focus on your nose while using your hands to rapidly move the head to either

side ("head thrust") can provide some information. Usually, individuals are

able to maintain good focus if the inner ears are intact since the head thrust

activates the VOR. Inability to maintain fixation when doing this indicates

damage to the inner ear.

Another test of vestibular function employs rotation of the patient in a

spinning chair (a Barany chair). It is very awkward to do this in the clinic

and creates considerable discomfort for the subject, particularly nausea.

Additionally, it cannot test each ear individually (since the whole head is

spinning and since both ears are moved simultaneously). Because of these

limitations, the use of a spinning chair has largely been replaced by caloric

testing, which is easier to carry out and tends to be less noxious. In addition,

only one horizontal canal is involved and therefore evaluated in routine

caloric testing, whereas both are involved in Barany rotation. Barany

rotation is more useful for testing the vertical canals; this can also be done

with bilateral simultaneous caloric testing with, however, some

inconsistency in the results. Vertical canal testing is rarely necessary, so a

rotating barber's chair need not be part of a physician's clinical

armamentarium.

Caloric testing

Caloric testing is an elegant method for evaluating the integrity of the

vestibular apparatus of each ear, independently. Caloric testing is carried

out most simply by irrigating the external auditory canal (observed by

otoscope to be unobstructed by wax, not infected, and with no tympanic

perforation) with water warmer or colder than body temperature, the

presumed resting temperature of the labyrinths. The differential warming or

cooling of the horizontal semicircular canal where it lies closest to the

external auditory canal causes a decrease or increase, respectively, in the

specific gravity of the endolymph at that point. If the head is positioned so

that the horizontal canal is vertical (see the position of the canal in Fig. 6-3),

significant convection currents are caused in the canal by the induced

changes in specific gravity (Figs. 6-4 and 6-5). Vertical upward currents are

caused by warming because of the decreased specific gravity and, with the

patient supine, the current in the horizontal canal is toward the ampulla and

crista (see Fig. 6-5). This direction of flow is excitatory to the crista, causing

increased firing over the pathways diagrammed in Figures 6-1, 6-2, and 6-5.

This results in vertigo (in which the patient feels that they are spinning

toward the ear being irrigated with warm water), and there will be VOR-

induced reflex movement of the eyes away from that ear. If the patient is

awake and alert, the drift of vision that is produced by the VOR will result in

a rapid corrective "jerk" of the eyes to try to keep them focused on a target.

Nystagmus is the result (remember, nystagmus is named by the direction of

the fast phase). Nystagmus "to the right" means nystagmus with the fast

component to the right. In order to maintain clarity, many examiners use the

term "right-beating" to clarify that they are referring to the direction of the

fast phase. Cold-water irrigation will have opposite effects. With the

horizontal canal in the vertical position (i.e., patient supine with their head

on a slight pillow), cold-water irrigation increases the specific gravity of the

endolymph closest to the external auditory canal. Therefore the fluid sinks

and a current is created away from the crista/ampulla (see Fig. 6-5). This

decreases the spontaneous firing of the ipsilateral horizontal canal

vestibular system and causes an imbalance with the resting tone of the

opposite horizontal canal system becoming dominant. The eyes are thus

driven tonically toward the irrigated side and the checking or fast

component is opposite in direction. This same nystagmus (and concomitant

vertigo) is seen in persons with destructive lesions of the vestibular

apparatus (see Fig. 6-2).

In performing caloric tests with warm water, 20 cc of approximately 48

degrees C water (higher temperature is painful) is irrigated into the external

auditory canal, which should be clear of wax, uninfected, and with no

tympanic membrane perforation (Fig. 6-6). Each auditory canal should be

irrigated separately for the same duration (30 seconds is convenient), and

the time of onset of nystagmus from the beginning of irrigation, as well as its

duration and direction should be recorded. The findings from the two sides

should be compared; a difference of approximately 20% is considered

significantly abnormal. At least five minutes should elapse between

irrigations to allow the stimulated canal to return to body temperature. The

patient should be asked whether s/he is experiencing spinning sensations or

nausea and whether there is a difference between the two sides. If there is

less vertigo on one side, you must consider that there is hypofunction of the

inner ear on that side.

You may have already surmised that vestibular-oculomotor testing has

considerable diagnostic usefulness in the unconscious patient since it is

objective and not dependent on patient cooperation. The vestibular-

oculomotor reflex pathway encompasses an expanse of the brain stem

(upper medulla through mesencephalon) that contains much of the reticular

formation necessary for the maintenance of consciousness. Caloric testing is

good at assessing the integrity of the brain stem (see Chap. 24). There are

two basic causes of depression of consciousness: diffuse bilateral

hemispheric dysfunction; or dysfunction of the brain stem reticular

formation (patients can have both). Caloric testing provides a method for

rapidly screening to determine which of these causes is producing the

depressed consciousness.

From our discussion of the mechanisms of the VOR it can be surmised

that the patient with an intact reflex has an intact brain stem. Also, since the

fast phase of nystagmus is mediated by activity in the cerebral cortex, a

vestibulo-ocular reflex with tonic eye deviation but no fast, corrective

movement, indicates that the brain stem is intact and that the cause of

depressed consciousness is diffuse cortical depression. This is most often

related to toxic, metabolic or drug-related effects. This occurs because the

brain stem response is more resistant to these effects than is cerebral

cortical function (of course, if brain activity is sufficiently depressed by toxic

or metabolic upsets, even the brain stem can be ultimately affected). In

cases of encephalopathy (i.e., depressed consciousness due to diffuse

cerebral cortical suppression), caloric irrigation thus elicits only tonic

deviation of the eyes. Warm caloric irrigation causes tonic conjugate

deviation of the eyes to the side opposite the irrigation, and cold irrigation

elicits deviation of the eyes toward the irrigated ear (Fig. 6-7A).

An interesting and important observation is the finding of normal

oculocephalic test results in the patient who is apparently in "coma". The

normal slow component of nystagmus indicates the integrity of the brain

stem and the normal rapid phase indicates that the cerebral cortex is awake,

alert and functional. Therefore this "coma" is actually fictitious and the

patient is more appropriately labeled as "catatonic".

Brain stem damage produces variable effects on the reflex depending on

the location of the reflex. For example, a destructive process (e.g.,

infarction, hemorrhage or tumor) at the midbrain level involves the

oculomotor complex with subsequent loss of the medial rectus portion of

conjugate horizontal deviation, with preserved lateral rectus deviation

during irrigation (Fig. 6-7B). A bilateral lesion of the pons, involving the

abducens nuclei and the proximate medial longitudinal fasciculi, destroys

the vestibular-oculomotor reflexes entirely (Fig. 6-7C). What effect would be

seen after complete transection of the basis pontis sparing the tegmentum

(see Figs. 4-5 and 6-1)?

"Doll's eyes"

The poorly named "doll's eye" maneuver is a simple mechanical test that is

particularly useful in the patient with depressed consciousness. More

appropriately called the oculocephalic maneuver, it is composed of a rapid

passive rotation of the head laterally, which causes an inertial flow of the

horizontal canal endolymph in the opposite direction of the head rotation. As

seen in Figure 6-8, the eyes are driven in a direction opposite the head

rotation.

If the patient is awake, the hemispheric checking component (this has

the same substrate as the fast component of the nystagmus) keeps the eyes

from deviating from midposition and actually may drive the eyes beyond the

midposition toward the direction of turning. If the patient is in a coma due to

bilateral hemispheric suppression, such as with toxic or metabolic disease

(e.g., sedative overdose or uremia), the checking component (also the fast

component of nystagmus) is lost. In this case, the eyes deviate away from

the direction of head rotation in an unchecked manner (the reflex response

is not inhibited by cerebral cortical input). Of course, if dysconjugate gaze is

produced during the maneuver, damage to the brain stem in areas that

control brain stem extraocular function must be assumed.

Conditions affecting vestibular function

There are a large number of conditions that can affect the vestibular

apparatus. Broadly, these can be divided into peripheral causes and central

causes. These two types of causes can often be distinguished on clinical

grounds (see below). Peripheral causes include conditions damaging the

inner ear or the vestibulocochlear nerve while central causes affect the

brain stem, vestibulocerebellum or, in rare cases, the cortex.

The most common cause of peripheral vertigo has been termed acute

labyrinthitis or vestibular neuronitis. While there may be subtle distinctions

between these conditions, the presumed etiology is inflammation. In this

condition the vertigo comes on quickly and patients often have severe

nausea and can't walk. They are at their worst in a matter of hours and then

there is slow improvement over days to weeks. There is usually no hearing

loss. If it comes on very rapidly (and particularly if there is hearing loss), you

should consider that the condition might result from infarction due to

occlusion of the labyrinthian artery. Meniere syndrome is not uncommon. It

is believed to result from obstructed drainage of endolymph, resulting in

increased pressure due to continued production. The pressure damages the

delicate hair cells (both vestibular and auditory) with loss of sensitivity. The

clinical course is punctuated by paroxysms of sudden vertigo (often with

worsened tinnitus), lasting hours with spontaneous resolution. This is

believed to occur due to sudden puncture of the membranes, with resolution

of symptoms dependent on sealing the puncture and reestablishment of the

normal equilibrium between the fluid compartments of the inner ear. These

attacks of vertigo (which can occasionally be triggered by loud noises) can

be violent enough to throw the patient to the ground, though, in between

attacks, there may be little residual other than some low-tone hearing loss.

Perilymph fistula is another cause of peripheral vertigo that is due to

leakage of fluid. This condition is often precipitated by barotrauma (abrupt

pressure changes) and individual attacks can occasionally be precipitated by

pressure changes (including Valsalva maneuver, coughing, sneezing,

airplanes, scuba diving, etc). Fluid usually leaks around the round window

into the middle ear (and can occasionally be seen there).

Acoustic neuroma (actually a neurolemmoma) is a common tumor that

grows on the vestibular nerve. Ironically, despite the fact that it damages

vestibular nerve fibers, it is a rare cause of vertigo. This is because it

progresses slowly, with ample time for compensation of deficits.

Positional vertigo will be discussed below.

Central causes of vertigo include damage to the brain stem or

vestibulocerebellum. Stroke, usually involving the posterior inferior

cerebellar artery (which supplies the lateral brain stem and part of the

cerebellum) often produces severe vertigo (along with diminished pain and

temperature sensations in the face). Isolated infarction or hemorrhage in the

cerebellum can produce vertigo. These are particularly important to

recognize because they can produce swelling and mass effect that can

occasionally be fatal due to brain stem damage. Both of infarction and

hemorrhage often produce occipital headache (particularly common with

hemorrhage). It is important to consider this before attributing vertigo to

vestibular neuronitis, which shouldn't produce headache.

Neoplasms of the cerebellum and brain stem usually don't produce

much vertigo (for the same reason of slow growth with compensation that

we invoked with acoustic neuroma). Inflammatory disease (such as MS or

rare conditions such as neurosarcoid) can produce vertigo although this is

usually not severe. Paroxysmal vertigo can result from the aura of migraine

or seizure. This is presumed to result from activation of the part of the

sensory cortex that perceives motion. If vertigo is the only symptom, it is

difficult to diagnose seizure or migraine until or unless more characteristic

features arise.

We will consider positional vertigo below.

Peripheral versus central vertigo

As can be seen in preceding section, there are quite different conditions

producing central and peripheral vertigo. Fortunately, it is usually possible

to distinguish central from peripheral vertigo on clinical grounds (Table 6-1).

First of all, acute central vestibular involvement (as contrasted with acute

peripheral disease) is associated with less severe vertiginous symptoms and

less nausea. Additionally, central disease often produces more severe

nystagmus than peripheral conditions. As distinct from central conditions,

where the nystagmus is out of proportion to the vertiginous sensations, with

peripheral conditions it is usually possible to predict how vertiginous the

patient is by examining the nystagmus. Furthermore, central vertigo often is

quite bizarre, changing directions depending on the way that the patient is

looking. That does not occur with peripheral vertigo, which is unidirectional

and most evident when the patient endevors to look in the direction of the

fast phase of the nystagmus. Vertical (upward or downward) nystagmus does

not occur with any normal lesion of the peripheral vestibular apparatus.

Therefore, vertical nystagmus must be presumed to be central. If not

present on forward gaze, vertical nystagmus is best observed by having the

patient look directly up or down (Fig. 6-9). Horizontal and rotary nystagmus

can occur with either peripheral or central disease and are therefore not of

value in differentiation.

Positional vertigo

Positional nystagmus and vertigo are relatively common disorders

associated which have several potential causes (both peripheral and

central). The patient complains of vertigo only when the head is in certain

positions, commonly looking up. The vertigo may persist if the head is kept

in the same position (this is particularly true with central disease) or it may

rapidly fade (typical of the more common peripheral disease). The most

common single cause of positional vertigo is so-called "benign paroxysmal

positional vertigo" (BPPV). The characteristic complaint is of vertigo, which

is severe and relatively brief, after turning in bed. This can also be triggered

by looking up, lying back, getting up quickly or bending to tie the shoes

(either when bending forward or, more commonly, when bringing the head

back up). This condition results from loose otoliths in the inner ear. When

these are in the semicircular canals, position-induced movement of the

stones can produce severe vertigo that resolves in under a minute (often

leaving the patient quite shaky and nauseated). This can occur after head

trauma but is increasingly common with age where the otoliths are less

securely anchored to the macula. Testing for positional nystagmus and

vertigo is done by rapidly dropping the patient backward as in Figure 6-10

(the Hall Pike or Barany maneuver). The patient's head is held right side

down, left side down, and in the midline on each of three trials. Vertigo and

attendant rotatory nystagmus are seen usually beginning after a few

seconds and terminating in less than a minute. The condition usually is self-

limiting (in months, with dissolution of the stones). However, the "canalith

repositioning maneuver" can often move these stones to a less sensitive part

of the inner ear, terminating the attacks. Some examples of etiologic

significance are head trauma, frequently of only minor severity,

vertebrobasilar distribution ischemia, and acoustic neurolemmoma, the

latter involving both the nerve directly and the brain stem by compression.

The most commonly affected individual is the elderly patient with no

predisposing factors and no threatening pathology. Presumably the

dysfunction, which is called benign positional vertigo, is caused by aging and

minor asymmetrical degenerative changes in the macula-otolith apparatus.

Cervical problems can produce positional vertigo by either of two

mechanisms: by impairing blood flow through the vertebral artery system; or

by activating sensory nerves from cervical muscles. With aging, cervical

osteoarthritis becomes common. Occasionally, the bony overgrowth

impinges on the transverse foramina through which the vertebral arteries

course. Turning the head may increase the foraminal narrowing and

compress the vertebral arteries to such a degree that brain stem ischemia

occurs. Vertigo on head turning may be the presenting symptom, but usually

other evidences of brain stem involvement clarify the picture. The vertigo

and other symptoms and signs should be reproducible by turning the head;

it is usually not necessary to go through the whole Barany maneuver (see

Fig. 6-10). In the case of vascular insufficiency, the vertigo and nystagmus

usually take significantly longer to develop than with other causes of

positional vertigo, up to 20-30 seconds. However, the nystagmus is variable

in type, persists for longer periods, and is associated with only mild vertigo.

It has been shown that sensory nerve fibers coming from the cervical

musculature have connections with the vestibular nuclei. These connections

probably mediate head-neck-trunk axis orientation information. Disorders of

the neck that are associated with abnormal muscle tightness or spasm can

produce vertigo with head movement even without impairing the circulation.

References

Brodal, A.: Neurological Anatomy in Relation to Clinical Medicine, ed.

2. New York, Oxford University Press, 1969.

Cogan, D.G.: Neurology of the Ocular Muscles, ed. 2. Springfield, IL,

Charles C. Thomas, Publisher, 1956.

Monrad-Krohn, G.H., Refsum, S.: The Clinical Examination of the

Nervous System, ed. 12. London, H.K. Lewis & Co., 1964.

Spillane, J.D.: The Atlas of Clinical Neurology, ed. 2. New York, Oxford

University Press, 1975.

Walsh, F.B, Hoyt, W.F.: Clinical Neuro-ophthalmology, ed. 3.

Baltimore, Williams & Wilkins Co., 1969.

Questions

Define the following terms:

conductive hearing loss, sensorineural hearing loss, tinnitus, vertigo,

nystagmus.

Conductive hearing loss is the loss of the ability to transmit sound waves to the inner ear.

Obstruction of the external ear, problems with the tympanic membrane or problems with

the middle ear (or the ossicular chain) are the cause.

Sensorineural hearing loss is hearing loss due to damage to the hair cells of the organ of

Corti or to the auditory part of the vestibulocochlear nerve.

Tinnitus is ringing or buzzing in the ears.

Vertigo is the illusion of movement.

Nystagmus is a to-and-fro movement of the eyes. It can be pendular (even swings in both

directions, often due to congenital vision problems) or can be Òjerk.Ó In jerk nystagmus,

there is a fast and a slow component, typically due to vestibular problems (the direction is

named by the fast component).

6-1. What brain lesions will cause loss of hearing in one ear?

Answer 6-1. It is nearly impossible to cause loss of hearing in one ear by damage to the

brain after the point at which the vestibulocochlear nerve enters the brain. This is

because the distribution of hearing is bilateral at all levels of the central nervous system

auditory pathway. Localization of sound may be slightly affected by auditory cortex

lesions. In fact it is nearly impossible for central nervous system lesions to cause clinically

detectable hearing loss and if these is hearing loss you must look at the conductive

system, the inner ear and the vestibulocochlear nerve.

6-2. What kind of hearing loss will be produced by damage to the inner ear?

Answer 6-2. Inner ear and CN VIII lesions will produce senorineural deafness.

6-3. What do you call problems in which the sound wave can not reach the

inner ear?

Answer 6-3. Blockage of the outer ear or damage to the tympanic membrane or middle

ear are called conductive deafness.

6-4. What would it mean if Weber's test lateralized to the left?

Answer 6-4. Weber's test lateralized toward the side of conductive deafness and away

from sensorineural.

6-5. What is the most common symptom of damage to the vestibular system?

Answer 6-5. Vertigo is common with vestibular damage.

6-6. What does it mean when someone says that nystagmus was in a

particular direction?

Answer 6-6. Nystagmus is named according to the direction of fast movement.

6-7. How can you distinguish vertigo from inner ear damage from that

causes by damage to the central nervous system?

Answer 6-7. With peripheral causes of vertigo (the illusion of movement), nystagmus is

proportional to the amount of vertigo and nystagmus is always in the same direction

regardless of the direction that the patient looks. Also, peripheral nystagmus is almost

never in a vertical (up or down) direction. With central vertigo (cerebellum, vestibular

nuclei and brain stem) nystagmus is usually greater than vertigo and may shift direction

depending on gaze direction.

6-8. What is the only way to examine the integrity of the vestibular system

on one side?

Answer 6-8. Caloric testing is the only way to check each inner ear vestibular function

independently.

6-9. What would you anticipate finding during cold-water caloric testing in

the intact patient who is awake?

Answer 6-9. When the patient is awake, the eyes will drift slowly toward the side of cold

water with rapid correction to opposite side (the opposite for warm water). There is tonic

balance in vestibular input from each ear; cold water caloric testing decreases tonic input

from the inner ear (warm water increases it).

6-10. What would you expect to find in the comatose patient whose brain

stem was still working if ice-water was infused into the right ear?

Answer 6-10. The eyes would drift toward the side of the ice-water infusion and remain

there for several minutes. There would be no nystagmus (which is a response generated

by the conscious cerebral cortex when the visual image slips across the retina).

6-11. Damage to the inner ear produces response that look like (cold/warm)

water caloric testing (choose one)?

Chapter 7 - Lower cranial nerve function

The lower cranial nerves are involved in pharynx and larynx function as well

as in movements of the neck and tongue. Damage usually manifests as

problems with speech and swallowing. These nerves arise from the medulla

and, in the case of the accessory nerve (CN XI), the spinal cord. These

nerves are commonly affected by conditions damaging the medulla but

bilateral damage to corticobulbar connections can create motor problems

that effect tongue and pharynx movement and speech.

IX, X. Glossopharyngeal and Vagus Nerves

These two nerves are considered together because exit from the brain stem

side by side, and have similar and frequently side-by-side and overlapping

functional and anatomical distributions in the periphery. Also, these nerves

connect with many of the same brain stem nuclei (dorsal motor nucleus of

the vagus, nucleus ambiguus, nucleus solitarius, spinal nucleus of the

trigeminal) and are often damaged together.

Pharynx and palate

The pharynx is innervated by nerves IX and X, with motor and sensory

contributions from both. In general, the vagus nerve is motor to the palate

elevators and constrictors of the pharynx (as occurs in swallowing and

gagging). The glossopharyngeal contains more sensory fibers, including

from the posterior part of the tongue and pharynx down to the level of the

larynx (where the vagus nerve begins to take over). The entire palate,

including the soft palate, has a sensory distribution from the maxillary

division of the trigeminal nerve.

Contraction of the paired and fused muscles of both sides of the soft

palate causes superolateral movement vectors (Fig. 7-1). The sum vector is

an upward, midline movement of the palate to seal the nasopharynx when

swallowing and making certain sounds (such as "guh"). When examining

palate elevation, look at the point of attachment of the uvula to see if it

remains in the midline. Also, if there is deviation, inspect the palate to make

sure this is not simply due to scaring of the soft palate due to prior throat

surgery. If the vagus nerve of one side is damage (e.g., by a tumor at the

jugular foramen), the palate elevates asymmetrically, being pulled up

toward the strong side (i.e., away from the weak side of the palate, Fig. 7-2).

If both sides of the palate are weak, as can occur in certain muscle

diseases or if the vagus is damaged bilaterally (such as from invasion by a

retropharyngeal carcinoma at the base of the skull), the palate does not

elevate normally during phonation and a hypernasal quality is imparted to

the voice (especially noted when making a "G" sound). Air usually emanates

from the nose when the patient tries to puff up the cheeks and liquid tends

to regurgitate into the nose when swallowing. Rarely, a similar finding of

bilateral weakness can be seen in patients with bilateral supranuclear

lesions (such as by bilateral cortical damage or bilateral damage to the

corticobulbar tracts. In this case, the patient will often show signs of

"pseudobulbar" affect (see Chapt. 5).

Gag reflex

The gag reflex involves a brisk and brief elevation of the soft palate and

bilateral contraction of pharyngeal muscles evoked by touching the posterior

pharyngeal wall. It is tested on the left and the right sides and the reflex

response should be consensual (i.e., the elevation of the soft palate should

be symmetrical regardless of the side touched). As with all reflexes, the gag

reflex has a sensory and a motor limb. The sensory limb is mediated

predominantly by CN IX. The motor limb by CN X. Touching the soft palate

can lead to a similar reflex response. However, in this case, the sensory limb

of the reflex is the trigeminal nerve. In very sensitive individuals, much more

of the neuraxis may be involved; a simple gag may enlarge to retching and

vomiting in some.

The gag response varies greatly from individual to individual but is

relatively constant in any one person. In some individuals, this reflex is

under such strong voluntary control that probing causes very little or no

response. This could make differentiation of normal suppression of the gag

from symmetric pathologic depression of motor and/or sensory function

difficult. However, actual damage can usually be determined by asking the

patient count to 10 immediately after rapidly swallowing 4 oz. of water. If

there were bilateral sensory and/or motor deficit, one would anticipate that

fluid would penetrate into the unprotected larynx, producing a "wet voice"

often with choking and coughing. The water-swallowing test is also a useful

screen in detecting which patients with neurologic deficit are likely to have

trouble eating (neurologic disease is more likely to affect swallowing of thin

liquids, like water, than it is to affect the wallowing of pudding

consistencies, which are easiest).

In glossopharyngeal nerve (sensory) involvement, there will be no

response when touching the affected side. With vagal nerve damage, the soft

palate will elevate and pull toward the intact side regardless of the side of

the pharynx that is touched. If both CN IX and X are damaged on one side

(not uncommon), stimulation of the normal side elicits only a unilateral

response, with deviation of the soft palate to that side; no consensual

response is seen. Touching the damaged side produces no response at all.

Larynx

The vagus nerve is both the sensory and motor innervation of the larynx.

Sensory and motor nerve fibers reach the larynx by different courses, with

the superior laryngeal nerve being sensory and the recurrent laryngeal

nerve being motor. The recurrent laryngeal nerves take a long, circuitous

route before reaching the larynx, with the left nerve passing all the way

around the aortic arch. Mediastinal lesions (e.g., carcinoma of the

esophagus, cancerous lymph nodes or aortic aneurysms) may be first

evidenced by hoarseness due to paralysis of the left vocal cord. The same

can be true on either side for malignancies in the neck, such as thyroid

cancer, since both the left and right recurrent laryngeal nerves pass

posterior to that gland to reach the larynx.

Loss of function of one or both recurrent laryngeal nerves causes

"hoarseness". Persistent, painless hoarseness should alert the examiner to

the possibility of unilateral or bilateral vocal cord weakness or paralysis.

This warrants examination of laryngeal appearance and function. This can

either be done by fiberoptic laryngoscopy or by indirect laryngoscopy with a

simple curved dental mirror and a light source (a bedside lamp shining over

the physician's shoulder or a flashlight held by an assistant) (Fig. 7-3). The

mirror must be warmed to prevent fogging. The tongue is held protruded

with cotton gauze or is depressed with a tongue blade, and the mirror is

then placed face down just below the soft palate, not touching the

pharyngeal walls to avoid gagging. It is sometimes useful to spray the

nasopharynx with a small amount of a weak topical anesthetic, such as 1%

Xylocaine. The mirror allows a view of the superior aspect of the larynx

covered by the epiglottis. The patient is asked to say "aah." The epiglottis

then uncovers the vocal cords, which should be in a relatively open position.

The patient then attempts to say "eee," a high pitched sound, the cords

should closely appose unless they are paralyzed on one or both sides (see

Fig. 7-3). Laryngoscopy (direct or indirect) is not part of a routine bedside

examination, however. It should be done only when phonation changes are

persistent.

Central vs. peripheral involvement

To differentiate between involvement of the peripheral portion of a cranial

nerve and the brain stem portions, it is important to consider whether there

is associated involvement of other cranial nerves or evidence of damage to

cerebellar functions or the tracts that course through the brain stem

(corticospinal or the lemniscal or spinothalamic sensory paths). It is unusual

for brain stem lesions to involve one or two cranial nerves in isolation,

without also affecting the contiguous long-tract and cerebellar system

structures. Motor neuron disease (a degenerative condition involving upper

and lower motor neurons) is an exception to this rule as is poliomyelitis (a

rare condition today).

Supranuclear motor pathways to the palate, pharyngeal, and laryngeal

musculature are bilateral. Therefore, unilateral lesions, even large strokes,

rarely produce any persistent problem with lower cranial nerve function

(there may be some transient swallowing trouble). Bilateral acute or

subacute loss of hemispheric connections to the medullary nuclei causes

difficulty with swallowing, phonating and, initially, a depressed gag reflex. In

time, the gag reflex may become uncontrollably hyperactive (as do many

other skeletal and autonomic reflexes when they are no longer under

supranuclear control).

Taste

Both the glossopharyngeal and vagus nerves (CN IX and X) have taste and

somatic sensory functions that are not routinely examined. However, the

taste function in the glossopharyngeal nerve (CN IX) can be examined if

there is suspicion of damage to the nerve (vagus nerve taste function can

not be tested). A saturated solution of salt, a substance normally tasted best

by the posterior and lateral taste buds (sweet is tasted best by the anterior

and midline tastebuds), is used in the testing with the same technique

described for the facial nerve (CN VII, see Chapt. 5).

Somatic sensation

The glossopharyngeal and vagus nerves (along with the facial nerve) supply

tiny sensory branches to the external auditory canal. This extensive overlap

(which also includes some contributions from the trigeminal nerve and the

2nd cervical nerve) precludes detecting loss of sensation caused by lesions

of any one of these nerves. However, pain in the ear may be a prominent

early symptom of irritation of any one of these cranial nerves. If the vagus or

glossopharyngeal nerve is involved, the pain often extends into the

pharyngeal region, helping to differentiate from the pain of seventh-nerve

irritation (which would be confined to the ear and mastoid region). If facial

weakness is present, this would be a clue to facial nerve irritation, while

depression of the gag reflex would suggest vagus or glossopharyngeal nerve

involvement. Trigeminal involvement is differentiated by pain in the face and

deficits in sensation in the trigeminal distribution; involvement of the upper

cervical nerves is indicated by hypoesthesia or pain in the scalp and upper

back of the neck.

Carotid sinus (baroreceptor) reflex

The baroreceptor reflex is mediated by sensory fibers in the

glossopharyngeal nerve and motor fibers in the vagus nerve. The normal

reflex detects increased blood pressure in the carotid sinus, triggering a

slowing of the heart and lowering of blood pressure. Because the receptor

works as a mechanical transducer, any kind of distortion of the carotid sinus

can cause slowing of the pulse and hypotension. Firm massaging of the

carotid bifurcation while monitoring pulse and blood pressure is the bedside

technique for testing the reflex. However, this is hazardous due to the

potential for excessive slowing of the heart and for disrupting any

athersclerotic plaque that might be in the carotid sinus region (potentially

producing embolic stroke).

XI. Spinal Accessory Nerve

Technically, the accessory nerve (CN XI) has two components: (1) a central

branch arising from medullary nuclei, and (2) a spinal accessory branch

arising in the first five to six cervical spinal segments from the lateral

portion of the ventral horn. The central branch joins the vagus immediately

after leaving the brain stem and is involved in innervation of the laryngeal

musculature. We typically consider this component with the vagus nerve and

have discussed examination of the larynx and pharynx (above).

The spinal accessory branch has an unusual course. It arises from motor

neurons in the upper 6 cervical segments. These neurons send their nerve

roots to exit the spinal cord laterally (not with the ventral motor nerve root).

The nerve roots that comprise the spinal accessory nerve ascend the

vertebral canal adjacent to the lateral side of the spinal cord and they enter

the skull by passing upward through the foramen magnum. This nerve then

turns laterally to pass through the jugular foramen along with cranial nerves

IX and X. The spinal accessory nerve provides the motor innervation of the

sternocleidomastoid (SCM) muscle before passing through the posterior

triangle of the neck to reach the trapezius muscle (which it also innervates).

Cervical nerves provide sensory innervation of these muscles.

When examining the SCM muscle, the bulk and outline of the muscle

should be observed. Atrophy is common in damage to the nerve and

fasciculations may be seen especially if the motor neurons are diseased. The

SCM muscle rotates the head away from the side of contraction. Testing

entails having the subject turn their head against the examiner's hand,

which is pressed against the patient's chin (Fig. 7-4). The bulk of the muscle

is then easily seen and palpated, and its strength can be determined. Having

the patient attempt to bring their chin toward their chest can test the left

and right SCM as they work together in this action. Paralysis of this muscle

will produce weakness, although not complete loss of ability to rotate the

head away from the lesion. This is because there are other muscles that are

able to partially compensate. For this same reason, the resting head position

is usually not affected by isolated SCM paralysis. Rarely, the patient will

hold their head turned slightly toward the side of lesion. The two

sternomastoids contracting together will flex the head toward the chest.

Bilateral weakness may prevent the patient from lifting their head off a

pillow and the head may be inclined posteriorly for lack of flexor tone.

Bilateral weakness suggests muscle or neuromuscular disease.

Spasmodic torticollis is a condition that often affects the tone of the

SCM muscle, although it can affect several other cervical muscles as well. In

this condition, there is an excessive activity of unknown etiology in one

(rarely both) of the sternomastoids. This results in an obvious deviation of

head postion. The subject's head is spasmodically turned away from the

involved muscle, which usually shows hypertrophy. One rather striking

observation is that the patient can often terminate the spasm by simply

touching the opposite side of the chin or cheek. The head drifts back into its

dystonic position once the touch is removed.

The spinal accessory nerve innervates the trapezius muscles, which

elevate the shoulders and rotate the scapula upward during abduction of the

arm. Denervation is evidenced by atrophy and often fasciculations. The

shoulder droops on the side of the weak muscle and there is downward

displacement of the scapula posteriorly. Shrugging the shoulders against

resistance is the standard way of testing the upper trapezius (Fig. 7-4).

Both the SCM and the trapezius muscles are under voluntary control,

requiring some input from the corticospinal system. The projections from

the cerebral cortex to the motor neurons innervating the SCM are bilateral.

Therefore, even large unilateral lesions do not produce weaknes of the SCM

or any deficits in head turning. However, in the case of corticospinal

innervation of trapezius motor neurons there is usually a contralateral

predominance. This contributes to mild to moderate contralateral weakness

of shoulder elevation following large, unilateral injuries of corticospinal

systems. This is rarely very severe, however

XII. Hypoglossal Nerve

The hypoglossal nerve (CN XII) has an entirely motor function, innervating

the muscles of the tongue. It originates from the columns of motor neurons

located near the midline in the dorsal aspect of the medulla. The nerve exits

the ventral side of the medulla as a row of small nerve rootlets adjacent to

the pyramid. After a short course through the subarachnoid space, the

rootlets come together as a single nerve that passes through the hypoglossal

foramen in the base of the skull. Ultimately it reaches the tongue and

innervates the intrinsic and extrinsic tongue muscles. The tongue is under

voluntary control. Accordingly, corticobulbar pathways activate hypoglossal

motor neurons. As with most cranial nerves, these corticobulbar projections

are bilateral, although there is a slight contralateral predominance.

Therefore, large lesions to the corticobulbar system, such as large strokes,

can produce slight weakness of the contralateral tongue.

Weakness of the tongue manifests itself as a slurring of speech. The

patient complains that their tongue feels "thick", "heavy", or "clumsy."

Lingual sounds (i.e., l's, t's, d's, n's, r's, etc.) are slurred and this is obvious

in conversation even before direct examination.

Examination of the tongue first involves observation for atrophy and

fasciculations. With supranuclear lesions, weakness, frequently mild, is not

accompanied by loss of muscle mass or fasciculations. Lesions of the nerve

(e.g., hypoglossal neurolemmoma, nasopharyngeal tumor along the base of

the skull, basal skull fracture) or of the nucleus in the brain stem (e.g.,

medullary stroke, motor neuron disease or bulbar poliomyelitis) the tongue

displays weakness, atrophy and, possibly, fasciculations on the side of the

involvement (Fig. 7-5). Atrophy and fasciculations in combination suggest

disease or damage to the motor neurons of the brain stem, but can be seen

with peripheral nerve damage, as well. Fasciculations are fine, random,

multifocal twitches of muscle. They are evaluated by observing the tongue

while it is at rest in the floor of the mouth. They are best seen along the

lateral aspect of the tongue. Protrusion frequently causes a fine tremor in

the normal tongue, which can obscure or mimic fasciculations. Simply

having the patient protrude their tongue in the midline tests strength of the

tongue. The normal vectors of protrusion are illustrated in Figure 7-5. When

one side of the tongue is weak, it protrudes toward the weakened side (Fig.

7-5). A repetitive or complex lingual sound (e.g., "la la la la" or "Methodist

artillery") often shows impediment when any part of the vocal apparatus is

affected (e.g., Broca's region, motor cortex, basal ganglia, cerebellum, brain

stem, nucleus, or nerve).

The most common process causing major involvement of the hypoglossal

nerve is motor neuron disease (amyotrophic lateral sclerosis). This is a

degenerative disease that has a predilection for early and severe

involvement of the hypoglossal motor neurons. The involvement is almost

always bilaterally symmetrical. Unilateral damage of the hypoglossal nerve

can be produced by tumors or trauma involving the base of the skull,

whereas stroke damaging corticobulbar projections is the usual cause of

unilateral supranuclear dysfunction.

References

Brodal, A.: Neurological Anatomy in Relation to Clinical Medicine, ed.

2. New York, Oxford University Press, 1969.

Cogan, D.G.: Neurology of the Ocular Muscles, ed. 2. Springfield, IL,

Charles C. Thomas, Publisher, 1956.

Monrad-Krohn, G.H., Refsum, S.: The Clinical Examination of the

Nervous System, ed. 12. London, H.K. Lewis & Co., 1964.

Spillane, J.D.: The Atlas of Clinical Neurology, ed. 2. New York, Oxford

University Press, 1975.

Walsh, F.B, Hoyt, W.F.: Clinical Neuro-ophthalmology, ed. 3.

Baltimore, Williams & Wilkins Co., 1969.

Questions

Define the following terms:

dysarthria, dysphonia, dysphagia.

Dysarthria is inability to speak clearly due to problems with control of the motor

apparatus of speech (generation and understanding of language should be normal and

reading/writing are unaffected).

Dysphonia is problems with speech due to disorders of the vocal apparatus in the larynx

(laryngitis is an example).

Dysphagia is difficulty with swallowing.

7-1. What are the main functions of the glossopharyngeal nerve?

Answer 7-1. The glossopharyngeal nerve provides sensation to the carotid barroreceptor

and chemoreceptor, the pharynx and the middle ear.

7-2. What would be the effect on soft palate movement of unilateral damage

to the vagus nerve?

Answer 7-2. The vagus nerve activates the elevator of the soft palate. The palate will

elevate with deviation of base of uvula away from the side of lesion (toward the intact

side).

7-3. What would be the effect of unilateral damage to the vagus nerve on

larynx function?

Answer 7-3. The vagus (recurrent laryngeal) innervates larynx muscle. Damage would

produce painless hoarseness with weakness or paralysis of vocal cord on that side.

7-4. Describe the course of the spinal accessory nerve.

Answer 7-4. The spinal accessory nerve comes from cervical spinal cord, enters the head

through formen magnum and exits through jugular foramen.

7-5. What does the spinal accessory nerve innervate?

Answer 7-5. CN XI innervates the SCM and trapezius muscles.

7-6. What does the hypoglossal nerve innervate?

Answer 7-6. The hypoglossal nerve innervates the tongue.

7-7. What would be the findings in unilateral damage to the hypoglossal

nerve?

Answer 7-7. The tongue deviates toward the side of weakness when protruded; it will be

weak when attempting to push against cheek on strong side of tongue and, with time,

there would be atrophy of the tongue on that side.

7-8. What would be the effect of a large stroke in the motor cortex on tongue

movement?

Answer 7-8. Corticobulbar damage (like a stroke) will slightly weaken the contralateral

side of the tongue.

7-9. What is the reflex pathway of the gag reflex?

Answer 7-9. Gag reflex - afferent is glossopharyngeal, efferent is vagus. It is a consensual

reflex.

7-10. What is the reflex pathway of the cough reflex?

Answer 7-10. The cough reflex - afferent is vagus, efferent is complex including

respiration centers and vagus.

7-11. What is the reflex pathway of the barroreceptor reflex?

Chapter 8 - Reflex evaluation

Reflexes are the most objective part of the neurologic examination and they

are very helpful in helping to determine the level of damage to the nervous

system. We will first discuss the various reflexes used in clinical practice and

will conclude the chapter with a discussion of the significance of the

findings. In some situations reflexes may be the major part of the

examination (e.g., the comatose patient). They have the value of requiring

minimal cooperation on the part of the patient and of producing a response

that can be objectively evaluated by the examiner. A list of all possible

reflexes would be almost endless and a tangle of eponymic jargon for those

with an historical bent. It is necessary to know the most commonly elicited

reflexes and this knowledge is not terribly difficult to acquire. However, the

interpretation of the reflex response requires some discussion. Table 8-1 is a

list of many reflexes, some of them in common clinical use (and some less

common). As a group, these reflexes can aid in evaluation of most of the

segmental levels of the nervous system from the cerebral hemisphere

through the spinal cord.

In this chapter we will discuss the evaluation of commonly tested

reflexes of the spinal cord. We have previously considered reflexes involving

the cranial nerves such as the pupillary light reflex, the jaw-jerk reflex, the

baroreceptor reflex and gag. We have also discussed reflex eye movements

and many of the autonomic reflexes (such as the oculocardiac and the

pupillary light reflex). Here we will consider muscle stretch reflexes and

superficial reflexes that are used to evaluate sensorimotor function of the

body.

All reflexes, when reduced to their simplest level, are sensorimotor arcs.

At the minimum, reflexes require some type of sensory (afferent) signal, and

some motor response. While the simplest of reflexes involve direct synapse

between the sensory fiber and the motor neuron (monosynaptic), many

reflexes have several neurons interposed (polysynaptic reflexes).

It is important to note that, even with the simplest of reflexes, there are

multiple inhibitory and facilitatory influences affect that can affect the

excitability of the motor neuron and thus amplify or suppress the response.

These influences can arise from various levels of the nervous system. There

are intrasegmental and intersegmental connections in the spinal cord, as

well as descending influences from the brain stem, cerebellum, basal ganglia

and cerebral cortices. All of these can influence the excitability of motor

neurons, thereby altering reflex response.

Lesions that damage the sensory or motor limb of a reflex arc will

diminish that reflex. This can occur at any level of the sensory or motor

pathway (in the case of the muscle stretch reflex, for example, this can

include: the peripheral nerve and receptors; the dorsal root or dorsal root

ganglion; the spinal cord gray matter; the ventral root; the peripheral nerve;

the neuromuscular junction; or the muscle).

Most of the pathways that descend the spinal cord have a tonic

inhibitory effect on spinal reflexes. For this reason, the net result of lesions

that damage the descending tracts is facilitation of reflexes that are

mediated at only the level of the spinal cord (a classic example being the

muscle stretch reflex). With few exceptions, this means that these spinally-

mediated reflexes become hyperactive. After acute lesions, spinal reflexes

often pass through an initial stage of hypoactivity. This stage has been called

"spinal shock" or diaschesis and is more severe and long lasting in

proportion to the degree of damage. For example, transection of the spinal

cord removes the greatest amount of higher influence and may be associated

with weeks of hypoactivity. Small lesions may have little effect on reflexes.

When reflexes return after spinal transection, they become extremely

hyperactive.

Some reflexes, such as the muscle stretch reflex, are semiquantitatively

graded. This is also true for some responses as the pupillary light reflex,

where the speed of reaction may indicate a "sluggish" response. On the

other hand, many reflexes are simply noted as present or absent. This is true

of the superficial reflexes (see Table 8-1) and the "primitive reflexes" that

are associated with diffuse bilateral hemispheric dysfunction. In this latter

case the reflexes are often designated as "dysinhibited" because these are

infantile responses that are suppressed in the normal adult nervous system.

Examination of myotatic ("deep tendon") reflexes

The muscle stretch (myotatic) reflex is a simple reflex, with the receptor

neuron having direct connections to the muscle spindle apparatus in the

muscle and with the alpha motor neurons in the central nervous system that

send axons back to that muscle (Fig. 8-1). Normal muscle stretch reflexes

result in contraction only of the muscle whose tendon is stretched and

agonist muscles (i.e., muscles that have the same action). There is also

inhibition of antagonist muscles.

Reflexes are graded at the bedside in a semiquantitative manner. The

response levels of deep tendon reflexes are grade 0-4+, with 2+ being

normal. The designation "0" signifies no response at all, even after

reinforcement. Reinforcement requires a maximal isometric contraction of

muscles of a remote part of the body, such as clenching the jaw, pushing the

hands or feet together (depending on whether an upper or lower limb reflex

is being tested), or locking the fingers of the two hands and pulling (termed

the Jendrassik maneuver). This kind of maneuver probably amplifies reflexes

by two mechanisms: by distracting the patient from voluntarily suppressing

the reflex and by decreasing the amount of descending inhibition.

The designation 1+ means a sluggish, depressed or suppressed reflex,

while the term trace means that a barely detectible response is elicited.

Reflexes that are noticeably more brisk than usual are designated 3+, while

4+ means that the reflex is hyperactive and that there is clonus present.

Clonus is a repetitive, usually rhythmic, and variably sustained reflex

response elicited by manually stretching the tendon. This clonus may be

sustained as long as the tendon is manually stretched or may stop after up to

a few beats despite continued stretch of the tendon. In this case it is useful

to note how many beats are present.

One sign of reflex hyperactivity is contraction of muscles that have

different actions while eliciting a muscle stretch reflex (for example,

contraction of thigh adductors when testing the patellar reflex or

contraction of finger flexor muscles when testing the brachioradialis reflex).

This has been termed "pathological spread of reflexes."

Practice observing normal reflexes in patients and initially among

students is an excellent way to determine the range of normalcy. Almost any

grade of reflex (outside of sustained clonus) can be normal. Asymmetry of

reflexes is a key for determining normalcy when extremes of response do not

make the designation obvious. The patient's symptoms may facilitate the

determination of which side is normal, i.e., the more active or the less active

side. If this is a problem, the remainder of the neurologic examination and

findings usually clarify the issue.

Decreased reflexes should lead to suspicion that the reflex arc has been

affected. This could be the sensory nerve fiber but may also be the spinal

cord gray matter or the motor fiber. This motor fiber (the anterior horn cell

and its motor axon coursing through the ventral root and peripheral nerve)

is termed the "lower motor neuron" (LMN). LMN lesions result in decreased

reflexes. The descending motor tracts from the cerebral cortex and brain

stem are termed the "upper motor neurons" (UMN). Lesions of the UMNs

result in increased reflexes at the spinal cord by decreasing tonic inhibition

of the spinal segment.

Lesions of the cerebellum and basal ganglia in humans are not

associated with consistent changes in the muscle stretch reflex. Classically,

destruction of the major portion of the cerebellar hemispheres in humans is

associated with pendular deep-tendon reflexes. The reflexes are poorly

checked so that when testing the patellar reflex, for example, the leg may

swing to-and-fro (like a pendulum). In normal individuals, the antagonist

muscles (in this example, the hamstrings) would be expected to dampen the

reflex response almost immediately. However, this is not a common sign of

cerebellar disease and many other signs of cerebellar involvement are more

reliable and diagnostic (see Chapt. 10). Basal ganglia disease (e.g.,

parkinsonism) usually is not associated with any predictable reflex change;

most often the reflexes are normal.

Superficial reflexes

Superficial reflexes are motor responses to scraping the skin. They are

graded simply as present or absent although markedly asymmetrical

responses should be considered abnormal as well. These reflexes are quite

different than the muscle stretch reflexes in that the sensory signal has to

not only reach the spinal cord, but also must ascend the cord to reach the

brain. The motor limb than has to descend the spinal cord to reach the

motor neurons. As can be seen from the description, this is a polysynaptic

reflex. This can be abolished by severe lower motor neuron damage or

destruction of the sensory pathways from the skin that is stimulated.

However, the utility of superficial reflexes is that they are decreased or

abolished by conditions that interrupt the pathways between the brain and

spinal cord (such as with spinal cord damage).

Classic examples of superficial reflexes include the abdominal reflex, the

cremaster reflex and the normal plantar response. The abdominal reflex

includes contraction of abdominal muscles in the quadrant of the abdomen

that is stimulated by scraping the skin tangential to or toward the umbilicus.

This contraction can often be seen as a brisk motion of the umbilicus toward

the quadrant that is stimulated. The cremaster reflex is produced by

scratching the skin of the medial thigh, which should produce a brisk and

brief elevation of the testis on that side. Both the cremaster reflex and the

abdominal reflex can be affected by surgical procedures (in the inguinal

region and the abdomen, respectively). The normal planter response occurs

when scratching the sole of the foot from the heel along the lateral aspect of

the sole and then across the ball of the foot to the base of the great toe. This

normally results in flexion of the great toe (a "down-going toe") and, indeed,

all of the toes. The evaluation of the plantar response can be complicated by

voluntary withdrawal responses to plantar stimulation.

The "anal wink" is a contraction of external anal sphincter when the skin

near the anal opening is scratched. This is often abolished in spinal cord

damage (along with other superficial reflexes).

"Pathological reflexes"

The best known (and most important) of the so-called "pathological

reflexes" is the Babinski response (upgoing toe; extensor response). The full

expression of this reflex included extension of the great toe and fanning of

the other toes. This is actually a superficial reflex that is elicited in the same

manner as the plantar response (i.e., scratching along the lateral aspect of

the sole of the foot and then across the ball of the foot toward the great toe).

This is a primitive withdrawal type response that is normal for the first few

months of life and is suppressed by supraspinal activity sometime before 6

months of age. Damage to the descending tracts from the brain (either

above the foramen magnum or in the spinal cord) promotes a return of this

primitive protective reflex, while at the same time abolishing the normal

plantar response. The appearance of this reflex suggests the presence of an

upper motor neuron lesion.

Evaluation of reflex changes

We now list the reflex changes associated with dysfunction at various

levels of the nervous system.

1. Muscle: Stretch reflexes are depressed in parallel to loss of strength.

2. Neuromuscular junction: Stretch reflexes are depressed in parallel

to loss of strength.

3. Peripheral Nerve: Stretch reflexes are depressed, usually out of

proportion to weakness (which may be minimal). This is because the

afferent arc is involved early in neuropathy.

4. Nerve root: Stretch reflexes subserved by the root are depressed in

proportion to the contribution that root makes to the reflex. Superficial

reflexes are rarely depressed since there is extensive overlap in the

distribution of individual nerve roots of the skin and muscle tested in the

superficial reflexes. However, extensive nerve root damage can depress

superficial reflexes in proportion to the amount of sensory loss in the

dermatomes tested or the motor loss in the involved muscles.

5. Spinal cord and brain stem: Stretch reflexes are hypoactive at the

level of the lesion and hyperactive below the level of the lesion. As

noted, during the initial state of spinal shock following acute lesions, the

spinal reflexes below the lesion are also hypoactive or absent.

o Superficial reflexes are hypoactive at and below the level of the lesion

and normal above. The abdominal superficial reflexes are not reliably

present in normal individuals who are excessively obese, who have

abdominal scars, or who have had multiple pregnancies, and they are

frequently poorly elicited in otherwise normal elderly persons. Therefore,

though classically depressed in persons with corticospinal system

involvement, one should not place great emphasis on depressed abdominal

reflexes if they are the only abnormality found in the examination. The

plantar response is exceptional and is abnormal, extensor (Babinski

response), when the descending tracts (upper motor neurons) are

involved.

6. Cerebellum: Classically the stretch reflexes are hypoactive and

pendular as mentioned above. When this is so, the test is reliable;

however, more often than not, the reflexes are not visibly abnormal.

7. Basal ganglia: There are no consistent deep-tendon or superficial

reflex changes. There may be the appearance of some of the "primitive

reflexes" (e.g., the glabellar, oculocephalic, grasp, and feeding reflexes

see Chap. 2) associated with some diffuse cerebral dysfunction

(dementia).

8. Cerebral cortex: Unilateral disease affecting motor cortex will

produce an upper motor neuron pattern of weakness (i.e., hyperactive

muscle stretch reflexes and depressed or absent abdominal and

cremasteric reflexes) on the contralateral side. Additionally, there may

be a Babinski response.

o Bilateral disease is associated with the same abnormalities bilaterally,

and in addition, there may be "primitive reflexes" due to release of these

responses from cortical inhibition (see Chap. 2).

o With bilateral damage to the motor cortex (particularly when

corticobulbar system is heavily affected), inhibitory control of the complex

emotional expression reflexes becomes defective. These individuals cry or

laugh with minimal emotional provocation and the patient usually says that

they do not understand why they are crying or laughing. These complex

emotional reflexes are subserved by the limbic system and are normally

under inhibitory modulation by the neocortex. Bilateral damage may

release these responses in a pattern that is termed "pseudobulbar" (see

Chpt. 5).

References

DeJong, R.N.: The Neurologic Examination, ed. 4. New York, Paul B.

Hoeber, Inc., 1958.

Monrad-Krohn, G.H., Refsum S.: The Clinical Examination of the

Nervous System, ed. 12, London, H.K. Lewis & Co., 1964.

Wartenberg, R.: The Examination of Reflexes: a Simplification.

Chicago, Year book Medical Publishers, 1945.

Questions

Define the following terms:

hyper-reflexia, pathological spread of reflex, clonus, Babinski sign,

Hoffmann's sign, myotatic reflex, upper motor neurons, lower motor

neurons, reinforcement.

Hyper-reflexia is excessively brisk reflexes

Pathological spread of reflex occurs when a reflex contraction occurs in a muscle whose

tendon was not stretched (i.e., finger flexion when testing the brachioradialis reflex or

thigh adduction when the patellar reflex is tested). It is a suggestions of hyperactive

reflexes.

Clonus is repeated contraction of muscles (usually the calf muscles or the wrist flexor

muscles) when the muscles are stretched manually (such as by ankle dorsiflexion or wrist

extension). Sustained clonus is when this occurs repeatedly as long as the stretch is

maintained.

Babinski sign is reflex dorsiflexion of the great toes and fanning of the other toes by

stroking the lateral side of the sole of the foot. This stroke is often continued across the

ball of the foot toward the base of the great toe. This occurs in patients with upper motor

neuron damage. The normal plantar response is for the treat toe to flex.

Hoffmann's sign is flexion of the thumb following a maneuver that consists first of passive

flexion of the patientÕs middle finger by pressure over the nail bed, followed by sudden

release of this pressure. It is a sign of brisk reflexes but is not pathological unless it is

accompanied by other signs of upper motor neuron damage or is asymmetrical.

Myotatic reflex is the muscle stretch reflex (often termed the deep tendon reflex).

Upper motor neurons are the principal descending motor pathways for voluntary

movement, including the corticospinal and corticobulbar tracts (and some other

associated tracts).

Lower motor neurons are the anterior horn motor neurons and their axons that extend

through the ventral nerve root and the peripheral nerves to reach the neuromuscular

junction.

Reinforcement involves the strong contraction of muscles outside of the area in which

muscle stretch reflexes are being tested. This will serve to increase the reflexes. Specific

examples include clenching the jaw, pressing the feet together or clasping the hands and

attempting to pull them apart (the Jendrasik maneuver).

8-1. What is the main effect of descending motor systems on reflexes?

Answer 8-1. Motor cortex and descending motor pathways generally involved in

suppressing (inhibiting) reflexes.

8-2. What are the 7 Deep Tendon Reflex exams (DTRs)? What sensory/motor

nerves are they testing?

Answer 8-2. Biceps - musculocutaneous nerve and mainly C6; Triceps - radial nerve and

mainly C7; Brachioradialis (radial periosteal) - radial nerve and mainly C6; Finger flexor -

musculocutaneous nerve and mainly C7-8; Patellar - femoral nerve and mainly L3-L4;

Achilles' reflex (ankle jerk) - tibial nerve and mainly S1; Jaw jerk - trigeminal

8-3. What are the superficial reflexes?

Answer 8-3. Superficial reflexes include: abdominal, cremaster, plantar, anal wink.

8-4. What is the effect of damage to corticospinal fibers on myotatic (deep

tendon) reflexes? What is the effect on superficial reflexes?

Answer 8-4. DTRs increase with damage to descending motor pathways; superficial

reflexes decrease with damage to descending motor pathways.

8-5. What primitive reflexes emerge with diffuse bilateral hemispheric

dysfunction?

Answer 8-5. Diffuse bilateral hemispheric dysfunction can dysinhibit grasp, glabellar,

suck, rooting, oculocephalic and nuchocephalic reflexes.

8-6. What happens to DTRs with lesions in the cerebellum & basal ganglia?

Answer 8-6. Usually no change, though may be sluggish with cerebellar damage.

8-7. How are DTRs graded?

Answer 8-7. 0-4+. To grade a reflex as "0", you must try reinforcement. 4+ means there

is sustained clonus. 1 is sluggish, 2 is "normal" and 3 is "brisk".

8-8. What is the most important consideration in testing reflexes?

Answer 8-8. Symmetry.

8-9. What reflex changes would occur in lesions of muscles?

Answer 8-9. No change unless end stage.

8-10. What reflex changes would occur in lesions of the neuromuscular

junction?

Answer 8-10. Normal to decreased depending on severity of weakness.

8-11. What reflex changes would occur in lesions of the peripheral nerves?

Answer 8-11. Decreased in clinically affected areas.

8-12. What reflex changes would occur in lesions of the nerve root?

Answer 8-12. Decreased in clinically affected areas.

8-13. What reflex changes would occur in lesions of the spinal cord and

brain stem?

Answer 8-13. Usually reflexes will be increased unless the gray matter (anterior horn

cells, lower motor neurons) is damaged right at the reflex level. Acute spinal cord injury

can result in spinal cord shock (flaccid, decreased reflex).

8-14. How can damage to sensory nerve fibers affect reflexes?

Answer 8-14. Damage to sensory nerve fibers may also decrease reflexes by damaging

the afferent limb of the reflex arc.

8-15. What is the effect of neuropathy on muscle stretch reflexes?

Answer 8-15. Neuropathy often produces decreased reflexes out of proportion to

weakness.

8-16. What are some visceral reflexes that can be tested?

Chapter 9 - Sensory system evaluation

Evaluation of sensation is hindered by several difficulties. Sensation belongs

to the patient (i.e., is subjective) and the examiner must therefore depend

almost entirely on their cooperation and reliability. A demented or psychotic

patient is likely to give only the crudest, if any, picture of their perception of

sensory stimuli. An intelligent, stable patient may refine asymmetries of

stimulus intensity to such a degree that insignificant differences in sensation

are reported, only confusing the picture. Suggestion can modify a subject's

response to a marked degree (e.g., to ask a patient where a stimulus

changes suggests that it must change and may therefore create false lines of

demarcation in an all too cooperative patient). Obviously the examiner must

not waste time and efficiency on detailed sensory testing of the psychotic or

demented patient, and must warn even the most cooperative patient that

minute differences requiring more than a moment to decipher are probably

of no significance. Additionally, the examiner must avoid any hint of

predisposition or suggestion. Nonetheless, even after all precautions are

taken, problems with the sensory exam still arise. Uniformity in testing is

almost impossible and there is considerable variability of response in the

same patient.

Factors that may affect the patient's variability and should be controlled

are fatigue and mood. Fatigue is particularly likely to be induced by a long,

detailed, unnecessary, and tedious sensory examination during which the

examiner is frequently exhorting the patient's undivided attention. A rapid,

efficient exam is the most practical means of diminishing fatigue. Mood is

less subject to modification.

Use of a pressure transducer, such as VonFrey monofiliments, allows

more consistent stimulus intensities and therefore more objectivity in the

examination; however, this is impractical at bedside and does not eliminate

patient variability.

Sensory changes that are unassociated with any other abnormalities

(i.e., motor, reflex, cranial, hemispheric dysfunctions) must be considered

weak evidence of disease unless a pattern of loss in classical sensory pattern

is elicited (for example, in a typical pattern of peripheral nerve or nerve root

distribution). Therefore, one of the principle goals of the sensory exam is to

identify meaningful patterns of sensory loss (see below). Bizarre patterns of

abnormality, loss, or irritation usually indicate hysteria or simulation of

disease. However, the examiner must beware of their own personal

limitations. Peripheral nerve distributions vary considerably from individual

to individual, and even the classic distributions are hard to keep in mind

unless one deals with neurologic problems frequently. Therefore, it is

advisable for the examiner to carry a booklet on peripheral nerve

distribution, sensory and motor (such as: Aids to the Examination of the

Peripheral Nervous System, published by the Medical Council of the U.K.).

Screening exam

As in all components of the examination, an efficient screening exam must

be developed for sensory testing. This should be more detailed when

abnormalities are suspected or detected or when sensory complaints

predominate. Basic testing should sample the major functional subdivisions

of the sensory systems. The patient's eyes should be closed throughout the

sensory examination. The stimuli should routinely be applied lightly and as

close to threshold as possible so that minor abnormalities can be detected.

Spinothalamic (pain, temperature and light touch), dorsal column (vibration,

proprioception, and touch localization), and hemispheric (stereognosis,

graphesthesia) sensory functions should be screened.

Pain (using a pin or toothpick), vibration (using a C128 tuning fork), and

light touch should be compared at distal and proximal sites on the

extremities, and the right side should be compared with the left.

Proprioception should be tested in the fingers and toes and then at larger

joints if losses are detected. Stereognosis, the ability to distinguish objects

by feel alone, and graphesthesia, the ability to decipher letters and numbers

written on skin by feel alone, should be tested in the hands if deficits in the

simpler modalities are minor or absent. However,

Significant defects in graphesthesia and stereognosis occur with

contralateral hemispheric disease, particularly in the parietal lobe (since

this is the somatosensory association area that interprets sensation).

However, any significant deficits in the basic sensory modalities cause

dysgraphesthesia and stereognostic difficulties whether the lesion or lesions

are peripheral or central. Therefore, it is difficult or impossible to test

cortical sensory function when there are deficits of the primary sensory

functions.

It may be surprising that the more basic modalities are usually not

greatly affected by cortical lesions. With acute hemispheric insults (e.g.,

cerebral infarction or hemorrhage), an almost complete contralateral loss of

sensation may occur. It is relatively short-lived, however; perception of pin

and light touch, as routinely tested, returns to almost normal levels, whereas

proprioception and vibration may remain deficient (though considerably

improved) in most cases. This lack of a significant long-term deficiency in

basic sensation following hemispheric lesions has no completely satisfactory

explanation, although some basic sensations probably have considerable

bilateral projection to the hemispheres.

Double simultaneous stimulation

Double simultaneous stimulation (DSS) is the presentation of paired sensory

stimuli to the two sides simultaneously. This can be visual, aural or tactile.

Light touch stimuli presented rapidly, simultaneously, and at minimal

intensity to homologous areas on the body (distal and proximal samplings on

extremities) may pick up very minor threshold differences in sensation.

Additionally, this testing can also detect neglect phenomena due to damage

of the association cortex.

Neglect may be hard to distinguish from involvement of the primary

sensory systems. However, neglect usually can be demonstrated in multiple

sensory systems (i.e., visual, auditory, and somesthetic), confirming that this

is not simply damage to one sensory system. Association cortex lesions,

particularly involvement of the right posterior parietal cortex, may become

apparent only on double simultaneous stimulation.

The face-hand test is a further modification of DSS. This test takes

advantage of the fact that stimuli delivered to the face dominate over

stimulation elsewhere in the body. This dominance is best illustrated in

children and in demented and therefore regressed patients. Before the age

of ten, most strikingly earlier than age five, stimuli presented simultaneously

to the face and ipsilateral or contralateral hand are frequently (more than

three in ten stimulations) perceived at the face alone. Perception of the

hand, and, if tested, other parts of the body is extinguished. In an older child

or adult, several initial extinctions of the hand may occur, but very quickly

both stimuli are correctly perceived. In the patient with diffuse hemispheric

dysfunction, dementia, a regression is frequently seen to consistent bilateral

extinction of the hand stimuli.

This test therefore can be doubly useful, first as an indication of diffuse

hemispheric function and second by stimulating the face and opposite hand,

a means of detecting minor hemisensory defects (e.g., if the patient

consistently extinguishes only the right hand and not the left, a sensory

threshold elevation due to primary sensory system or association cortex

involvement on the left is suspect).

Patterns of sensory loss

Since one of the main goals of the sensory exam it is important to consider

the principle patterns of sensory loss resulting from disease of the various

levels of the sensory system. These patterns of loss are based on the

functional anatomy of the various components of the sensory system and we

will also briefly review some of these elements.

Peripheral neuropathy (polyneuropathy)

Peripheral neuropathy, that is, symmetrical damage to peripheral nerves, is

a relatively common disorder that has many causes. Most of these can

broadly be classified as toxic, metabolic, inflammatory or infectious. In this

country, the most common causes are diabetes mellitus and the malnutrition

of alcoholism, although other nutritional deficiencies or toxic exposures

(either environmental toxins or certain medicines) are occasionally seen.

Infections, such as Lyme disease, syphilis or HIV can cause this pattern and

there are inflammatory and autoimmune conditions that can produce this

pattern of damage. A more complete discussion can be found in chapter 12.

Because this is a systemic attack on peripheral nerves, the condition

produces symmetrical symptoms. The initial symptoms are most often

sensory and the longest nerves are affected (the ones that are most exposed

to the toxic or metabolic insult). The receptors of the feet are considerably

farther removed from their cell bodies in the dorsal root ganglia than are the

receptors of the hands. The metabolic demands on these neurons is

substantial which accounts for their being the first affected and for the early

appearance of sensory loss in the feet in a "stocking" distribution. Later on,

as the symptoms reach the mid-calf, the fingers are involved and a full

"stocking-glove" loss of sensation develops. Even later, when the trunk

begins to be involved, sensory loss is noted first along the anterior midline

(Fig. 9-1).

Vibration perception is often the earliest affected modality since these

are the largest, most heavily myelinated and most metabolically demanding

fibers. Usually the loss of pin, temperature, and light-touch perception

follow, and conscious proprioception (joint position sense) is variably

affected. Despite the fact that proprioception follows many of the same

pathways as vibration it is usually not as noticeably affected because the

testing procedure (i.e., moving the toes or fingers up or down), is quite

crude and is not likely to pick up early loss.

The peripheral deep-tendon reflexes are depressed early in most cases

of peripheral neuropathy, particularly the Achilles reflex. This is because the

sensory limb of this reflex depends on large myelinated fibers.

As a rule, symptomatic motor involvement is late and, when it occurs, it

affects the intrinsic muscles of the feet first.

Radiculopathy

Radiculopathy (nerve root damage) is the relatively common result of

intervertebral disc herniation or pressure from narrowing of the

intervertebral foramina due to spondylosis (arthritis of the spine). The most

common presentation of this is sharp, shooting pain along the course of the

nerve root (Fig. 9-2). Single-root usually does not have any sensory loss

because of the striking overlap of dermatomal sensory distribution (Fig. 9-3).

There may be slight loss, often accompanied with paresthesias (tingling or

pins and needles) in small areas of the distal limbs where the sensory

overlap is not great. Table 9-1 lists some of the common areas of paresthesia

or decreased sensation with common nerve root injuries. Herpes zoster,

which affects individual dorsal roots, nicely demonstrates dermatomal

distribution because, despite the lack of sensory loss (attributable to

overlap), vesicles ("shingles") appear at the nerve endings in the skin (see

Fig. 9-3).

Nerve root damage in the cauda equina often produces a "saddle"

distribution of sensory loss by affecting the lower sacral nerve roots. This

saddle distribution of sensory loss can also be seen in anterior spinal cord

damage (see the next section) and, in either case, must be taken quite

seriously due to the potentially serious sequellae of spinal cord and cauda

equina damage.

Nerve root pain is often quite characteristic. It is often quite sharp and

well-localized to the dermatomal distribution and may be brought on by

stretching of the nerve root (Fig. 1-5) or by maneuvers that load the

intervertebral discs and compress the intervertebral foramina (Fig. 1-4).

However, pain can also "refer" (see Chapt. 26). This referred pain is less

localized and is often felt in the muscles (myotomal) or skeletal structures

(sclerotomal) that are innervated by the nerve root. The person usually

complains of a deep aching sensation. Myotomes should not be memorized

but can be looked up easily by referring to the motor root innervations of

muscles, which are essentially the same as their sensory innervations.

Sclerotomal overlap is so great that localization on their basis is impractical.

Spinal cord

Spinal cord damage is characterized by both sensory and motor symptoms

both at the level of involvement as well as below by affecting the tracts

running through the cord. Symptoms referable to the level of injury appear

in the pattern of dermatomes and myotomes and, when present, are very

useful for localizing the level of spinal cord damage. The symptoms of

damage to the long sensory tracts (the dorsal columns and the spinothalamic

tract) are less helpful in localizing the lesion because it is often impossible to

determine the precise level of the sensory loss and also because, particularly

in the case of the spinothalamic tract, there is considerable dissemination of

the signal in the spinal cord before it is relayed up the cord. Similar

difficulties make it difficult to localize the level of spinal cord damage by

examining for damage to the descending (corticospinal) motor tracts.

Therefore, when long tract damage is identified, one can only be certain that

the lesion is above the highest level that is demonstrably affected.

Compression of the spinal cord from the anterior side first involves the

spinothalamic paths from the sacral region, and a "saddle" loss of pin and

temperature perception is usually the first symptoms even with lesions high

in the spinal cord (Fig. 9-4). In this case, as symptoms progress with greater

degrees of compression, symptoms progressively ascend the body up toward

the level of the actual cord damage (see Fig. 9-4).

Intramedullary lesions of the spinal cord (such as syrinx, ependymoma,

or central glioma) may present with a very unusual pattern of "suspended

sensory loss". This consists of an isolated loss of pain and temperature

perception in the region of the expanding lesion because of damage to the

crossing spinothalamic tract fibers (Fig. 9-5). In this pattern of sensory loss

due to expanding intramedullary lesions, there is "sacral sparing" of pain

and temperature because the more peripheral spinothalamic fibers (the ones

from the sacrum) are the last to be involved (see Fig. 9-4). With

intramedullary lesions, the dorsal columns are also usually spared until

extremely late in the course of expansion, leaving touch, vibration, and

proprioception intact. The loss of one or two sensory modalities (such as

pain and temperature sense, in this case) with preservation of others (such

as touch, vibration and joint position sense) is termed a "dissociated sensory

loss" and is in contrast to the loss of all sensory modalities associated with

major nerve or nerve root lesions or with complete spinal cord damage.

Complete hemisection of the cord is seen occasionally in clinical

practice and is quite illustrative of the course of spinal cord sensory

pathways. This lesion results in a characteristic picture of sensorimotor loss

(Brown-Sequard syndrome), which is easily recognized due to the loss of

dorsal columns sensations (vibration, localized touch, joint position sense)

on the ipsilateral side of the body and of spinothalamic sensations (pain and

temperature) on the contralateral side (Fig. 9-6).

Brain stem

Brain stem involvement, like involvement of the spinal cord, is characterized

by long-tract and segmental (cranial nerve) motor and sensory abnormality

and is localized by the segmental signs. The picture of ipsilateral cranial

nerve abnormality and contralateral long-tract dysfunction is quite

consistent (Fig. 9-7). Both the dorsal columns and pyramids decussate at the

spinomedullary junction (the spinothalamic system has already decussated

in the spinal cord). This accounts for the typical crossed presentation of

symptoms in the body. Below the level of the midbrain, the spinothalamic

and dorsal column (medial lemniscus) systems remain separate and

therefore lesions may involve the pathways separately (i.e., there may be a

dissociated sensory loss). For example, an infarction caused by occlusion of

the posterior inferior cerebellar artery typically involves only the lateral

portion of the medulla. The ipsilateral trigeminal tract and nucleus and the

spinothalamic tract are frequently included in the lesion, leaving a loss of

pain and temperature perception over the ipsilateral face (see Chap. 5) and

the contralateral side of the body from the neck down. The medial lemniscus

and its modalities (i.e., vibration, joint position and well-localized touch) are

spared.

Thalamus

Thalamic lesions are associated with contralateral hemihypesthesia. Initially,

if the lesion is acute, there is considerable loss bordering on anesthesia, but

some recovery is expected over time, especially of touch, temperature, and

pain perception. Vibration and proprioception remain more severely

affected. Unfortunately, episodic paroxysms of contralateral pain may be a

striking and not infrequent residual of thalamic destruction (this is one of

the "central pain syndromes"). The pain can be controlled occasionally with

anticonvulsants. An additional residual that may develop over time is

marked contralateral hyperpathia in spite of the presence of diminished

overall sensitivity of the skin. Stimulation of a site with a pin causes a very

unpleasant, poorly localized and spreading sensation, which is frequently

described as burning. This is presumably an irritative phenomenon of the

nervous system, although it may also result from loss of normal pain-

suppression mechanisms. It is seen most often after thalamic lesions,

although it can occur as a residual of lesions in any portion of the central

sensory systems. A hypersensitivity to cold sensation frequently

accompanies the hyperpathia.

Cerebral cortex

As discussed earlier, cortical lesions tend to leave minimal deficits in basic

sensation but, especially if the parietal lobe is damaged, there may be

striking contralateral deficits in the higher perceptual functions (see Chap.

2). Stereognosis and graphesthesia are abnormal in spite of minor

difficulties with vibration and proprioception and even less, if any, difficulty

with pain, temperature, and light-touch perception. Of course, if there is

significant deficit of primary sensations, it may be impossible to test for

deficits of higher perceptual functions.

References

Brodal, A.: Neurological Anatomy in Relation to Clinical Medicine,

ed.2, New York, Oxford University Press, 1969.

Medical Council of the U.K.: Aids to the Examination of the Peripheral

Nervous System. Palo Alto, Calif., Pendragon House, 1978.

Monrad-Krohn, GH, Refsum, S.: The Clinical Examination of the

Nervous System, ed. 12, London, H.K. Lewis & Co., 1964.

Wolf, J.: Segmental Neurology, Baltimore, University Park Press,

1981.

Questions

Define the following terms:

conscious proprioception, agnosia (sterioagnosia), graphesthesia,

dermatome, sclerotome, myotome, radiculopathy, myelopathy,

anesthesia/hypoesthesia, hyperpathia, allodynia, hyperesthesia,

dysesthesia, paresthesia, polyneuropathy, subjective.

Conscious proprioception is the ability to tell where a body part is in space. It is largely

based on joint position sense.

Agnosia (sterioagnosia) ia the inability to recognize what a sensation is despite relatively

normal perception of the sensation. When it is tactile it is termed sterioagnosia (or

asteriognosis). It would be the inability to determine the denomination of a coin despite

normal ability to perceive it, for example.

Graphesthesia is the ability to identify letters or figures traced on the skin (without

looking).

Dermatome is the area of skin supplied by a nerve root.

Sclerotome is the area of bone and joints supplied by a single nerve root.

Myotome is the muscles supplied by a single nerve root.

Radiculopathy this is damage to a nerve root (radiculitis is irritation).

Myelopathy is damage to the spinal cord from any cause.

Anesthesia/hypoesthesia is loss (or decrease) in sensation.

Hyperpathia is the exaggerated perception of normally painful stimuli.

Allodynia is the perception of normally innocuous stimuli as being painful.

Hyperesthesia is excessive sensitivity to any modality.

Dysesthesia is the perception of the pain when no stimulus is present.

Paresthesia is the detection of a sensation in the absence of any stimulus.

Polyneuropathy is generalized damage to peripheral nerves. This is usually due to a

systemic cause.

The sensory exam is by definition subjective, that is, relies on the patients report.

9-1. What are the steps involved in the sensory exam?

Answer 9-1. First, the exam needs to determine if the patient can detect modality; next,

you need to know if it is the same on both sides; then you need to know if the patient can

interpret the sensation.

9-2. How is it possible to lose some types of sensations and not others?

Answer 9-2. Different sensory modalities follow different types of nerve fibers and

different pathways (tracts) through the nervous system.

9-3. What sensations are conveyed by the small-diameter sensory nerve

fibers in a peripeheral nerve?

Answer 9-3. Small, unmyelinated or lightly-myelinated (slow) nerve fibers convey pain

and termperature sense.

9-4. What sensations are conveyed by large-diameter sensory nerve fibers in

a peripeheral nerve?

Answer 9-4. Large, heavily myelinated (fast) nerve fibers convey proprioception and well-

localized touch sensation. They are also the sensory limb of the muscle stretch reflex.

9-5. What sensations are conveyed by the dorsal columns?

Answer 9-5. Dorsal columns convey vibration, 2-point discrimination and joint position

sense.

9-6. What sensations are conveyed by the spinothalmic tract?

Answer 9-6. The spinothalamic tract conveys pain, temperature and very light (poorly

localized) touch.

9-7. What is tested by double simultaneous stimulation?

Answer 9-7. Double simultaneous stimulation tests attention/neglect (parietal lobe).

9-8. Where would the lesion be if the patient was able to detect all

modalities of sensation but could not recognize an object placed in the right

hand?

Answer 9-8. The left parietal lobe (somatosensory association area).

9-9. What is the common sensory loss from damage to the spinal cord?

Answer 9-9. Spinal cord lesions often result in sensory level (loss of sensations below

lesion) due to damage to ascending sensory tracts. .This loss (especially of pin sensation)

usually begins at least several segments below the level of the lesion of the tract.

9-10. What would be the expected sensory loss from damage restricted to

the left side of the spinal cord?

Answer 9-10. There would be ipsilateral loss of vibration and joint position sense and

contralateral loss of pain and temperature sense below the level of the lesion. The pain

and temperature sense loss would start at least several dermatomes below the injury.

9-11. What is the characteristic of sensory loss due to damage to peripheral

nerves in a limb?

Answer 9-11. Peripheral nerve injury (mononeuropathy) usually results in well-localized

sensory loss (often with appropriate motor loss).

9-12. What is the pattern of sensory loss seen in diffuse damage to

peripheral nerves (polyneuropathy?

Chapter 10- Motor system examination

In this chapter we discuss the evaluation of the motor systems, that is the

systems involved in generation and control of voluntary and reflex

movements. The motor system can be divided into (1) the peripheral

apparatus, which consists of the anterior horn cell and its peripheral axon,

the neuromuscular junction, and muscle, and (2) the more complex central

apparatus, which includes the descending tracts involved in control (i.e., the

pyramidal system) and the systems involved in initiating and regulating

movement (the basal ganglia and cerebellum).

Dysfunction in individual components of the motor system systems

results in fairly specific abnormalities that can be evaluated at the bedside.

Although multiple components may be involved (particularly with diseases of

the central nervous system) isolated involvement of the various components

commonly occurs. We will consider these components in order to help you

establish an orderly approach to motor system evaluation (Table 10-1).

Examination for motor dysfunction includes assessment of strength,

muscle tone, muscle bulk, coordination, abnormal movements and various

reflexes. Many of these are best detected through simple (but careful)

observation. However, a few maneuvers aid in the detection of abnormality.

Table 10-2 lists the components of a comprehensive and efficient screening

examination that will elicit and localize most motor system dysfunctions. If

no abnormalities are found, this exam should only take two to three minutes

in a cooperative patient. Table 10-3 lists the findings expected with diseases

listed in Table 10-1, and Table 10-4 lists differentiating points between

diseases affecting the nerves versus those primarily damaging muscle.

Elements of the examination

Examination of the motor system can be relatively objective and Tables 10-2

and 10-3 outlines an approach using isolated segments of the motor system

as models. Mixed-system involvements do occur with variable symptom and

sign predominance, depending on such variables as the dominance of the

various motor systems involved and the extent of the lesion(s) in each

system. Lack of cooperation caused by patient fatigue, misunderstanding of

the tasks demanded, or lack of physician-patient rapport must always be

considered. Feigned or hysterical weakness, for example, usually can be

distinguished by its bizarre localization, the absence of expected

involvement of other systems (i.e., reflex, sensory, cranial), and the irregular

ratchet-like giving way of muscles tested. It is always important to consider

the implications of your findings and what additional or confirmatory test

can be done to clarify and document your conclusions about the patient's

motor system abnormality.

Strength

Strength is conveniently tested by having the patient resist your force as you

attempt to move their body part against the direction of pull of the muscle

that you are evaluating. This is graded on a graded scale of 0-5, with "0"

representing absolutely no visible contraction and “5” being normal. A grade

of "1" means that there is visible contraction but no movement;"2" is some

movement but insufficient to counteract gravity;"3" is barely against gravity

(with inability to resist any additional force); and "4" being less than normal

(but more than enough to resist gravity). Obviously, there is ample range

between 3 and 5, making the determination somewhat subjective. Some

examiners expand the 5 point scale into a 9 point scale by the addition of

“+” symbols when strength seems to be between numbers. Still others add

“-“ symbols when a muscle seems to function just below a level. While there

may be merit in having a scale beyond the original 5 points (particularly

between 3 and 5) it must be remembered that the scale is quite arbitrary

and lacks the precision suggested by the creation of many categories.

Additionally, "normal" is a designation that takes into account the patient’s

age and level of conditioning. This assessment can be made with greater

precision when there is a normal side with which to compare it.

In order to test strength at various levels of the nervous system, several

muscles must be tested. The more common of these muscles, along with

their particular peripheral nerve and nerve root levels, are found in Table

10-5.

It is often very efficient to test patients using functional tasks rather

than by manually testing each muscle. For example, the patient may be

asked to hold the arms horizontally out in front with the palms up and eyes

closed. Diffuse weakness of the upper limb often produces a “pronator drift”,

i.e., downward drift of the weak limb with the hand pronating (turning in). If

the limb drifts straight down, without pronation, this is not suggestive of

physiologic weakness and the patient may have a conversion disorder or

malingering. Erratic drift of the limb can be seen with proprioceptive

sensory loss (confirmed by testing of proprioception). When testing strength

in the legs it is helpful to have the patient attempt to walk on the toes and

then heels. Other tests of the legs would include hopping on each foot,

standing from a chair (without use of the hands) or climbing a stair. These

latter tests examine more proximal muscles.

When confronting the patient with weakness, some assessment of effort

should be made. Poor effort is usually reflected as good initial contraction,

followed by a collapse (often termed "breakaway" or “collapsing” weakness).

This is not a pattern seen in true neurologic injury where strength is

typically inadequate but relatively constant. It is usually easy to detect the

patient with "collapsing" weakness if you apply varying force during the

muscle test. With true neurologic weakness, the maximum force that the

patient applies does not vary appreciably. "Collapsing weakness" should not

be graded. There are several potential causes of collapsing weakness,

ranging from pain to the conscious embellishment of symptoms. When this

pattern is seen, other more objective elements of the examination (such as

reflex testing) become more important.

The ultimate goal of strength testing is to decide whether there is true

"neurogenic" weakness and to determine which muscles/movements are

affected. In correlation with the remainder of the motor exam it should be

possible to determine the particular part of the nervous system that is at

fault to produce this weakness. Probably the most important decision is

whether the weakness is due to damage to upper or lower motor neurons

(UMN or LMN). As you may recall from chapter 8, upper motor neuron

weakness is due to damage to the descending motor tracts (especially

corticospinal) anywhere in its course from the cerebral cortex through the

brain stem and spinal cord. UMN weakness is typically associated with

increased reflexes and a spastic type of increased tone. On the other hand,

LMN weakness is due to damage of the anterior horn cells or their axons

(found in the peripheral nerves and nerve roots). This results in decreased

stretch reflexes in the affected muscles and decreased muscle tone.

Additionally, atrophy usually becomes prominent after the first week or two,

and this atrophy is out of proportion to the amount of disuse produced by

the weakness.

"Deep tendon" (myotatic) reflexes

The "deep tendon" (myotatic) reflexes are a critical part of the neurologic

examination that is discussed in Chapt. 8. Testing reflexes is the most

important element of determining whether weakness is of an upper or lower

motor neuron type (limited only by the fact that only certain muscles

actually have reliably tested stretch reflexes (include the biceps, triceps,

brachioradialis (radial periosteal), quadriceps, hamstring and calf muscles).

Since the reflex arc includes stretch receptors and sensory fibers, it is not

necessary to damage motor axons to abolish reflexes. However, in the

setting of the patient with known weakness, reflex testing is a powerful tool

to investigate the cause.

As you may recall from chapter 8, symmetry of reflexes is the most

important consideration in determining normality. Pathological "spread of

reflexes" (i.e., contraction of muscles that produce motions other than the

one associated with the test muscle) is another objective sign of

hyperactivity. You may recall that sustained clonus (repeated muscle

contraction when a muscle is passively stretched) is an indicator of

hyperactive reflexes.

Conditions that damage lower motor neurons decrease muscle stretch

reflexes by interrupting the reflex arc (Fig. 8-1). Therefore, a diminished

reflex in a weak muscle suggests damage to the lower motor neurons

somewhere along the course to the muscle (i.e., anterior horn cells, motor

nerve root, or peripheral nerve). Hyperactive reflexes are seen after damage

to upper motor neurons (i.e., descending motor tracts). There are other

confirmatory findings that may suggest upper or lower motor neuron

disease. These signs include atrophy (LMN), fasciculations (LMN), spasticity

(UMN), Babinski sign (UMN) or loss of superficial reflexes (UMN).

Superficial and "pathologic" reflexes

Superficial reflexes (abdominal, cremaster and plantar) are discussed in

chapter 8. These reflexes are mediated above the spinal cord. Therefore,

disruption of the spinal cord or brain stem can abolish these reflexes. Of

course, the superficial reflexes can also be abolished if there is extensive

damage to sensory nerves or lower motor neurons in the region.

The "Babinski response" (upgoing toe) is the classic pathological reflex

seen with upper motor neuron damage. This reflex replaces the normal

plantar response. The findings upon testing of superficial reflexes should be

placed in the context of the remainder of the motor exam when evaluating

upper and lower motor neurons.

Muscle Bulk

Muscle bulk is primarily assessed by inspection. Symmetry is important,

with consideration given to handedness and overall body habitus.

Generalized wasting or cachexia should be noted and may reflect systemic

disease, including neoplasia. Some areas can be adequately evaluated by

inspection alone, such as the thenar and hypothenar regions or the shoulder

contour. Some areas, like the thigh, leg, arm and forearm, may be better

evaluated by measurement. These measurements can also permit

assessment over time.

Severe atrophy strongly suggests denervation of a muscle (such as with

LMN lesions). This usually begins at least a week after acute injury and gets

progressively worse with time (unless reinnervation takes place). Atrophy

due to LMN damage must be distinguished from that which occurs

secondary to disuse. However, there is usually a clear substrate for disuse

(bedrest, cast, etc.) and there is little overall change in strength.

Unfortunately, patients who have limited functional reserve (such a those

with prior neural disease or the elderly) can be severely affected by disuse

and deconditioning.

Coordination

Coordination is tested as a part of a sequence of movements. Typically the

patient is asked to hold his/her hands in front with the palms up, first with

the eyes open and then closed (as when examining pronator drift, above). It

is usually good form to instruct the patient to prevent movement of his/her

hands, and to exert some force either toward the floor or in attempting to

push the hands apart. This force can be used to assess the strength of the

patient and then should be released suddenly and without warning. After a

short excursion, the patient should check this movement, and this checking

should be symmetrical. The patient may then be asked to touch his/her nose,

and subsequently the examiners finger. This can be repeated a few times to

assess the smoothness and accuracy of the movement. Further assessment

can be obtained by having the patient perform a rapidly repeated movement

such as tapping the thumb and forefinger together, or by having the patient

clap his hands. This test can be made somewhat more difficult by having the

patient repeatedly strike first the palmar and then the dorsal aspect of one

hand against the palm of the other. This, of course, must be done with each

hand, and you are evaluating rhythmicity and speed in performance of the

movement.

Lower extremity coordination can be tested in the supine position by

having them attempt to place the heel of one foot on the opposite knee and

subsequently tap or slide the heel down the shin to the ankle. This should be

done with each leg. Other tests of lower limb coordination include tapping of

the foot on the examiner’s hand, or attempting to draw a number in the air

with his/her foot. If the patient can stand and walk, it is usually only

necessary to evaluate gait in order to assess lower limb coordination. The

patient who can stand on either foot for ten seconds without excessive sway

does not need further testing of leg coordination.

These maneuvers test several neurologic systems. Strength is required

for all of these tests. Excessive rebound (or loss of checking) is suggestive of

cerebellar injury on the side of the abnormality. Similarly, difficulty with

rapid alternating movements (dysdiadochokinesia) or marked overshoot or

undershoot when attempting to hit a target (intention tremor) suggests

cerebellar problems on that side. Repetitive over and undershoot during

voluntary movement may reflect as "intention tremor". Extreme slowness of

movement can be produced by extrapyramidal disease (such as Parkinson’s).

Of course, problems with any part of the motor systems may affect

coordination. For example, if there is a marked alteration in muscle

strength, muscle tone, or if the patient is having abnormal movements this

can influence your perception of coordination. Therefore, although tests of

coordination are mainly directed toward assessing cerebellar function, you

must decide whether other problems in the motor system are affecting these

tests.

Muscle Tone

Muscle tone may be increased or decreased, with increased tone being

much easier to detect. Tone can be assessed by one of two means. The most

common method is for the examiner to passively move the patient’s limb

(especially at the wrist). The second method involves evaluating arm swing

(with the patient standing). Tone is often easily checked by having the

patient stand with his/her arms hanging loosely at their side. When the

patient’s shoulders are moved back and forth or rotated the arms should

dangle freely. Increased tone is usually reflected as the arms being held

stiffly both in the standing position and when walking. The lower limbs can

be evaluated with the patient seated with the legs dangling. Movement of

the feet should result in gentle swinging of the legs of a brief duration.

Increased tone results in abrupt restriction on the excursion of the feet.

There are two common patterns of pathologically increased tone,

spasticity and rigidity. Spasticity is found with upper motor neuron injuries

and manifests as a marked resistance to the initiation of rapid passive

movement. This initial resistance gives way and then there is less resistance

over the remaining range of motion (clasp-knife phenomenon). Rigidity is an

increase in tone that persists throughout the passive range of motion. This

has been termed "lead pipe" rigidity and is common with extrapyramidal

disease, especially Parkinson’s disease.

Many older individuals have paratonia. This is a phenomenon in which

the patient is essentially unable to relax during passive movements. You will

note that the resistance is irregular and generally greatest when you change

the pattern of movement. Of note, most of these individuals have apparently

normal tone when you test them in a standing position and move their

shoulders about (as described above). Extreme paratonia is common in

patients with dementia.

Some types of increased tone appear to be prolongations of voluntary

muscle contraction. Myotonia is a slowness of relaxation of muscles after a

voluntary contraction or a contraction provoked by muscle percussion. This

is a disorder of striated muscle and not an abnormality of innervation and

may be seen in conditions such as myotonic dystrophy or congenital

myotonia (a disorder of ion channels). Occasionally, metabolic diseases of

muscle (such as hypothyroidism) can result in myotonic discharges.

Myotonia can be easily observed by asking the individual to reverse a

muscle action quickly (i.e., trying to rapidly open a tightly clenched fist) or

by tapping on a muscle belly (such as the thenar muscles). Neuromyotonia is

a rare condition of irritability of the nerve (possibly autoimmune) where

there is persistent contraction. Muscle contractions are not terminated and

the patient becomes "stiff" with movement.

Abnormal movements

There are a number of types of abnormal movements including tremor,

chorea, athetosis, dystonia, hemiballism and fasciculations. Each of these

has clinical implications that require discussion.

Tremor is the most common abnormal movement seen in practice. Three

characteristics are of particular importance. These include the symmetry (or

asymmetry) of the tremor, the rate of the tremor (basically, whether it is fast

or slow, i.e., greater or less than 7 cycles per second) and the circumstances

under which the tremor is present (i.e., whether it is worst at rest, during

sustained postures or when moving). Physiological tremor comes in two

types. Rapid (>7cps) tremor is characteristic of states with increased

sympathetic function (think of the last time you had too much coffee). This is

most commonly secondary to anxiety, but may occur with increased

adrenaline (such a pheochromocytoma) or thyrotoxicosis. A slower tremor

must be classified with regard to the conditions in which it is most evident.

If it is present predominantly at rest, and decreases with movement, this

suggests extrapyramidal disease such as Parkinson’s disease (PD). In PD,

the tremor is frequently asymmetrical and is usually associated with other

signs (bradykinesia, rigidity or delayed postural corrections). Tremors which

are severe on sustained postures (such as with the hands outstretched), but

which may worsen slightly with action are characteristic of essential tremor

(this is also seen in “senile” tremor or familial tremor). These tremors are

absent at rest and are often worsened by anxiety. They are often

asymmetrical and characteristically affect the use of writing and eating

implements. Damage to cerebellar systems (particularly the hemispheres or

dentate connections) often produces a tremor that is most pronounced

during voluntary actions.

The second most common type of abnormal movement that is seen in

practice is fasciculation. These are twitches in muscle (actually, contraction

of a single motor unit, i.e., all of the muscle fibers attached to a single motor

neuron). These can be felt and often seen. These are random and involuntary

occurrences and do not result in movement of a joint. Fasciculations may

reflect damage to lower motor neurons, either the cell body or the motor

axon located in the nerve root or peripheral nerve. Of course, if the

fasciculations were due to LMN lesions one would expect some weakness,

decreased tone and (after a while) atrophy. Also, one would expect that the

fasciculations would remain in a single group of muscles for more than

transiently. Fasciculations may also be a finding in muscle overuse, or a sign

of local muscle irritation. Also, there are some individuals who have “benign

fasciculations” particularly in the calf muscles. Of course, these are not

associated with weakness or other motor system abnormalities.

There are several other, less common abnormal movements. Chorea is a

rapid, fleeting, random and non-stereotyped movement which is worsened

by anxiety and which can be suppressed for short periods by conscious

effort. They differ from tics since tics are stereotyped and repeat within the

same muscle groups. Tics may affect the voice, as well, and consist of

repeated throat clearing, sniffing or coughing. Multiple vocal and motor tics

are seen in Tourette syndrome. Athetosis is a slow, writhing, snakelike

movement of a body part or parts. Dystonia is a sustained twisting of the

body, usually the trunk or neck (where it is called torticollis). Hemiballism is

a flinging motion of one side of the body, potentially resulting in falls.

Involuntary movements are seen in a number of clinical situations.

Chorea, athetosis and hemiballism are reflections of basal ganglia disease.

This may be congenital (a type of cerebral palsy), post infectious

(Sydenham's chorea), hereditary (Huntington's chorea), metabolic (Wilson's

disease) or cerebrovascular.

Station

This is the ability to maintain an erect posture. One should be able to stand

both with the eyes open and closed with a relatively narrow base of support

(the feet close together). You should record excessive sway, falling to one

side, or marked worsening in the ability to stand when the eyes are closed.

Excessive sway with the eyes open is common with cerebellar or

vestibular problems. This may be to one side (and commonly is with

vestibular disorders) or may be to both sides (especially with conditions that

effect the midline portion of the cerebellum, such as intoxication). You must

consider the possibility of other explanation such as the patient not have

enough strength to stay upright or severely delayed reactions to

destabilization (such as with Parkinson’s disease). Some patients can stand

well with the eyes open, but have marked increase in instability with the

eyes closed. This is suggestive of a disorder of conscious proprioception (i.e.,

joint position sense, as may be seen with peripheral neuropathy or dorsal

column/medial lemniscus dysfunction). This is termed a Romberg sign.

Proprioceptive problems on one side can be brought out with standing on

one foot. Of course, there are other tests of conscious proprioception,

including evaluation of joint position and vibration sense in the feet. These

data must be correlated with the findings on station.

Gait

This is an important part of any neurologic exam. It is particularly important

to observe the symmetry of the gait, the ability to walk with a narrow base,

the length of the stride when walking at a normal pace, and the ability to

turn with a minimum of steps and without loss of equilibrium. When

observing a normal person from behind, the medial parts of the feet strike a

line and there is no space visible between the legs at the time of heel strike.

This is a narrow-based gait and deviation from this can be measured in the

amount of distance laterally each foot strikes from the line that their body is

following. Tandem walking (the ability to walk on a line) may be used to

evaluate for stability of gait, recognizing that many normal elderly patients

have trouble with this.

Damage to virtually any part of the nervous system may be reflected in

gait. An antalgic gait, or the limp caused by pain is familiar to any

practitioner. Patients with unilateral weakness may favor one side, and if the

weakness is spastic (i.e., from upper motor neuron damage) the patient may

hold the lower limb stiffly. S/he will drag the weak limb around the body in a

"circumducting" pattern. A staggering or reeling gait (like that of the drunk)

is suggestive of cerebellar dysfunction. Generally, the patient with true

vertigo will tend to fall to the one side repeatedly (especially with the eyes

closed). A patient with foot drop will tend to lift the foot high (steppage

gait). Hip girdle weakness often results in a "waddle," with the hips shifting

toward the side of weakness when the opposite foot is lifted from the floor

(of course if both sides are weak the hips will shift back and forth as they

take each step). Patients with Parkinson's disease often have difficulty

initiating gait. The steps are usually short though the gait is narrow-based. If

severe, the patient may be propulsive (they may even fall). Patients who are

"glue footed" (sliding their feet along the ground rather than stepping

normally) may be suffering from damage or degeneration of both frontal

lobes or the midline portion of the cerebellum. When damage to these areas

is severe the patient may be severely retropulsive (tending to fall over

backwards repeatedly). Dorsal column injury may result in a gait in which

the patient "stamps" his or her feet, and usually also needs to look at the

feet in order walk. Patients with painful neuropathy of the feet may walk as

if they are "walking on eggs" and patients with spinal stenosis may walk

with a stooped posture (a "simian" posture).

Disorders of the motor systems

The reflection of motor system disease depends on the particular part of the

motor system that is involved. Here we will discuss the characteristic

deficits produced by each level of the motor system.

Muscle disease (see Chapt. 12)

Typically, muscle disease (myopathy) has its earliest and greatest effects on

proximal musculature. There is little atrophy (until very late) and deep-

tendon reflexes are decreased only in proportion to the weakness. Certain

metabolic myopathies may result in cramping due to the fact that energy is

required to relax muscles and myotonia may also produce difficulty in

relaxation. There are no sensory changes in myopathy.

Neuromuscular disease (see Chapt. 12)

Myasthenia gravis is the prototypical neuromuscular disease. This condition

results from autoimmune damage to acetylcholine receptors, which results

in inefficient neuromuscular transmission. Initial contraction is strong but

during sustained contraction, depletion of neurotransmitter results in

progressive weakness. This can be seen during tonic actions (like simply

holding up the eyelids or maintaining the arms out in front) or in actions

that require sustained activity (like talking or swallowing a meal). For

further information see Chapt. 12.

Lower motor neuron (LMN) disease (see Chapt. 12)

These conditions occur due to damage to the anterior horn cells, the ventral

roots or the peripheral nerves anywhere along their course to the muscles.

In the majority of cases, the weakness is distal. The best explanation for the

predominantly distal weakness in neuronal disease is that longer motor (also

sensory) nerve fibers are more exposed and vulnerable to the many

processes that damage nerve. An exception to this rule is the diffuse

polyneuropathy of Guillain-Barre syndrome (presumed to be an autoimmune

process). In this case weakness may begin in the proximal muscles and this

is presumable because the primary damage to nerves is occurring quite

proximally (near the nerve root level).

LMN disease results in weakness in the muscles connected with the

affected nerve fibers. Understanding of the distribution of nerves and nerve

roots to the individual muscles is essential to correct interpretation (Table

10-5). Additionally, there is atrophy (after the first week or two following an

acute injury) that is out of proportion to simple disuse. Furthermore,

reflexes are usually affected quite early and severely. This is because most

conditions that damage LMNs also damage sensory nerve fibers that

represent the afferent limb of the muscle stretch reflex. Finally, when there

is damage to LMNs in peripheral nerves, there is often an accompanying

sensory loss that can aid in diagnosis of the nerve that is involved.

Upper motor neurons (UMN)

Historically, this has been associated with the corticospinal (pyramidal)

tract. However, this is not quite accurate since voluntary motor pathways

arising in the cerebral cortex can function by activating more primitive

descending tracts from the brain stem. It is clear that the direct projections

in the corticospinal tract are responsible for highly skilled movements,

especially of the hands. In this section we will refer to direct and indirect

corticospinal projections to distinguish the corticospinal tract itself from the

indirect activation of other descending motor tracts by cerebral cortical

input. Additionally, it must be understood that the motor cortex does not act

independently, but rather under the influence of the premotor cortex

(involved in planning and initiating movement) as well as "extrapyramidal"

systems such as the basal ganglia and cerebellum (see below).

The classic picture of acute damage to UMNs includes contralateral

paralysis of distal limb movements, while proximal limb movements are

severely weakened and trunk movement minimally involved. Muscle tone

(measured as passive resistance to manipulation) is depressed in this initial

phase. The deep-tendon reflexes are also likely to be absent, recovering over

time to normal or hyperactive levels. The superficial reflexes (abdominal and

cremasteric) opposite the lesion are depressed or absent. A Babinski

response is often present on the weak side.

Over weeks to months proximal strength improves to a significant

degree, whereas distal movements make only a poor recovery. A

rudimentary grasping capability is frequently all that remains in the hand.

Extension, opposition, and individual finger movements remain severely

affected or lost. Presumably, the recovery of proximal functions relates to

some bilaterality of distribution of corticospinal fibers that innervate

proximal muscles. The modest recovery of distal movements is suspected to

relate to preserved motor pathways from the brain stem (presumably under

extrapyramidal control).

Damage to the precentral gyrus (primary motor cortex) or isolated

damage to the medullary pyramid produces a rather pure corticospinal tract

lesion. In these cases, the weakness of distal muscles is severe but there is

little appearance of other findings such as spasticity and hyperreflexia that

are hallmarks of most UMN lesions. Other UMN lesions also damage

indirect descending connections between the cerebral cortex and spinal

cord. This happens with lesions of the premotor cortex, corona radiata,

internal capsule, cerebral peduncle, basal pons, and lateral columns of the

spinal cord. Invariably, lesions in these areas also involve other cerebrofugal

pathways that are intermixed with the direct corticospinal (pyramidal)

projection. In all of these cases (in addition to the weakness), there is a

decrease in tonic inhibition of reflexes and an increase in resting muscle

tone. This is accompanied by hyperactivity of the deep-tendon reflexes and

development of what is traditionally called spasticity.

Spasticity is elicited during passive manipulation of the muscles. The

muscles at rest do not have excessive tone but any brisk stretch of a muscle

group (particularly the flexors in the upper extremity and the extensors in

the lower extremity) will result in a "catch" at about midlength of the muscle

followed by a sudden release of the catch and relaxation of the muscle. The

last two components, the catch and release, have been likened to a closing

pen knife, which is the origin of the term "clasp-knife" spasticity.

Hyperactive deep-tendon reflexes and spasticity have a similar mechanism

(overactive muscle stretch reflexes). The giving away or release portion of

the clasp-knife phenomenon is presumed to be caused by increased firing of

the inhibitory Golgi tendon organs, which produce an overactive reflex to

inhibit the muscle.

If the lesion extends beyond the confines of the traditional corticospinal

path, more descending pathways are involved and a greater degree of

spasticity is noted; also there is a poorer recovery from weakness. This is

presumably because of loss of more inhibitory influences on the segmental

reflex arc and loss of more facilitatory influences on the motor neuron

effector systems.

After very acute lesions of the descending motor systems there is often

initial flacid weakness that is sometimes followed by stereotyped movements

and postures (decorticate posture, decerebrate posture or generalized

withdrawal reactions)(Fig. 10-1). Acute destructive lesions of the descending

motor pathways cause a transient shock state of flaccid, areflexic paralysis.

When progressively greater amounts of the descending pathways are

involved, a longer period of shock ensues. Acute cortical destruction may

result in only hours to days of shock, whereas acute transection of the spinal

cord can cause a shock state that persists for many weeks to months before

spastic hyperreflexia and rudimentary spinal reflex behavior return. The

precise pathophysiology of spinal shock is not clear, but it may complicate

the evaluation of the patient following acute injury. It is always difficult to

predict the final extent of the neurological injury in the setting of shock.

Chronic or slowly progressive destruction of the descending motor pathways

is not associated with a shock state. Presumably this is because

compensatory reorganization of the motor function occurs in pace with the

losses.

Lesions that extensively destroy the cerebral cortex and basal ganglia,

and preserve at least some of the diencephalon (like those caused by severe

hypoxia) may result in stereotyped motor responses that involve flexion of

the upper extremities and extension of the lower extremities. Noxious

stimulation is usually necessary to elicit this reflex activity, which has been

called decorticate posturing (Fig. 10-1). It has been thought, on the basis of

experimental data, that release of the rubrospinal motor system is, at least

in part, responsible for decorticate posturing.

Transection of the brain stem, for example by stroke, at the level of the

midbrain or pons is followed after a period of neuraxis shock by severe

spasticity and reflex extension and pronation of the upper extremities with

extension of the lower extremities and trunk on noxious stimulation (see Fig.

10-1). This response is called decerebrate posturing and depends on

preservation of the vestibular nuclei in the caudal brain stem, with the

extension being produced by vestibulospinal pathways.

Lesions transecting the lowest portion of the brain stem or the upper

spinal cord result in quadriplegia and severe spasticity after a period of

shock. In time, reflex flexion movements can be elicited with noxious

stimulation (see Fig. 10-1). These probably represent primitive spinal

withdrawal responses.

As a rule, UMN lesions affect large areas of the body below the level of

injury. It is often difficult to localize the specific level of damage by the

pattern of weakness. Associated neurologic findings may clarify the level.

For example, cranial nerve involvement or involvement of nerves or nerve

roots may indicate a brain stem or spinal cord level of involvement,

respectively, while cortical findings such as language difficulties, visual field

abnormalities, dyspraxias, or other disorders of higher integrative function

suggest cortical damage. In most UMN lesions, the whole side of the body

below the lesion is affected (hemiparesis or hemiplegia). However, in the

cerebral cortex the motor representation for the arm, face, and trunk lie

within the supply of the middle cerebral artery, whereas the leg lies within

the distribution of the anterior cerebral artery (Fig. 10-2). Loss of middle

cerebral cortical perfusion therefore causes a greater degree of weakness of

the upper extremity than of the lower extremity. Occlusion of the anterior

cerebral artery, an uncommon event, is associated with greater weakness in

the leg than in the arm.

Because sensory and motor systems are near one another through the

spinal cord, most of the brain stem and the cerebral hemispheres, it is

common to have some sensory as well as motor symptoms. The sensory

abnormality (see Chapt. 9) may help localize the lesion. Pure involvment of

UMNs without any sensory damage is most often seen with small lesions

(usually vascular) in the posterior limb of the internal capsule or in the base

of the pons.

Basal Ganglia

The abnormalities associated with lesions and degenerative processes in the

basal ganglia are discussed in some detail in Chapter 18. The findings are

generally categorized into "hyperkinesias" and "hypokinesias". The classic

picture of parkinsonism (the most common cause being Parkinson disease)

includes bradykinesia (slow movements), rigidity, difficulty initiating

movements and delayed postural corrections. These symptoms all fall into

the category of "hypokinesia". There may also be a tremor at rest

(suppressed by movement), which is a form of hyperkinesia. The rigidity of

parkinsonism is present in all ranges of passive manipulation and cannot be

abolished by sectioning the dorsal roots. Therefore, it is not due to reflex

overactivity (deep tendon reflexes are normal in parkinsonism). It is

probably due to tonic overactivity of the descending motor pathways and it

can be abolished by cutting descending motor tracts (see Chap. 18). Other

types of "hyperkinesia" include chorea, athetosis, hemiballism, tic and

dystonia. These are indicative of dysfunction of the basal ganglia

(extrapyramidal) system. However, they are not diagnostic of a particular

cause (see Chap. 18).

Cerebellum

Cerebellar disease produces predominantly motor symptoms. There are

three main parts of the cerebellum, which have slightly different functions.

The lateral cerebellar hemispheres (the neocerebellum) are involved in

controlling distal limb movement of the ipsilateral limbs. The vermis of the

cerebellum (midline) is involved in control of axial functions as well as the

voice and eye movements. The posteroinferiorly-located vestibulocerebellum

(floculonodular lobe; archicerebellum) is involved in vestibular functions and

regulation of the vestibulo-ocular reflex (see Chapt. 6).

Damage to the neocerebellum produces predominant symptoms of

tremor, ataxia, and hypotonia. The tremor is of a particular type, consisting

of rhythmic, variably 3-8 per second oscillations that occurs predominantly

on voluntary activity and reaches its peak of oscillation toward the end of

the movement. It disappears with posturing or at rest. It is noticed

dramatically when reaching for objects (such as when performing finger-to-

nose testing. The ataxia (incoordination) is manifest in several ways. There

is dysmetria (past-pointing) with overshoot and/or undershoot of the target.

Also, there may be lack of checking (excessive rebound). For example, if the

patient is asked to hold their hand extended out in front of them while

pressure is applied and then suddenly released, there will be excessive

movement before the patient "checks" the motion. Additionally, the patient

will have difficulty performing a rapidly repeated motions (tapping fingers,

patting hands or tapping feet) and this may be even more obvious if there is

rapid alternating movements involved in the motion (such as pronation and

supination of the hands). Ataxia of the legs is manifest in difficult in walking,

often characterized by a broad-based and/or drunken gait.

Diosrders affecting the midline cerebellum (vermis) effect axial motor

activity. This is likely to be manifest as head and trunk instability as well as

speech and eye movement problems. The problems with trunk stability are

usually brought out during attempts to stand still or to walk. When there is

both instability of the trunk and ataxia of the legs patients will have severe

ataxia. After vermal lesions, the speech may sound drunken or

inappropriately staccato and eye movements may be erratic and

uncoordinated when patients have damage to the vermis.

Because it is an important symptom of cerebellar disease, it would be

appropriate to say a few more words about ataxia. Cerebellar ataxia is fairly

easy to observe in the office and it has at least two origins: (1) intention

tremor of the legs, giving a dysmetric gait, and (2) truncal imbalance. If it is

advanced, the patient has a wide-based compensatory gait, and if there is

lateralized limb involvement, they tend to lean and fall toward the affected

side. A sensitive test for ataxia is heel-to-toe tandem walking; this should be

part of any neurologic screening examination in a patient with gait or

balance complaints because it detects early cerebellar dysfunction. If the

trunk alone is involved, as in early alcoholic degeneration or with a tumor of

the vermis, there is a tendency to fall to either side, forward or backward.

Some persons with midline cerebellar damage may have a stronger tendency

to fall backward. This is called retropulsion and can also be seen in basal

ganglia dysfunction (particularly parkinsonism) and in frontal lobe disorders.

When retropulsion is due to cerebellar involvement, it frequently has an

involuntary tonic character, i.e., the patients actually appear to be actively

pushing themselves backward. Even at rest, sitting or standing, there is a

tendency to lean or fall backward. With frontal lobe dysfunction and

parkinsonism, the retropulsion is usually passive rather than active, i.e., the

patient has difficulty recovering from being pushed backward or from a

backward-leaning position, but he has no active or forced retropulsion at

rest.

Damage to the vestibulocerebellum (flocculonodular lobe;

archicerebellum) produces vestibular findings, including nystagmus that

may be quite severe and in different directions depending on which way the

patient is looking ("gaze-shifting nystagmus"). This is often more severe than

symptoms due to vestibular damage since vestibulocerebellar damage is

more difficult to compensate for.

Finally, cerebellar damage can occasionally be reflected in hypotonia.

The examiner should check for tone abnormalities by asking the patient to

relax and not resist. The limbs are then moved rapidly by the examiner in

several ranges. A lack of resistance or a floppiness is noticed with hypotonia.

Having the patient sit with his legs swinging free may test the legs. The leg

is lifted by the examiner and released. Normally the leg swings back and

forth several times and then stops, arrested by inertia and the normal

resting muscle tone, which is a manifestation of the sensitivity of the normal

muscle stretch reflex. With cerebellar hypotonia, the leg swings freely,

unchecked, like a pendulum, arrested mainly by passive limb inertia.

References

Brodal, A.: Neurological Anatomy in Relation to Clinical Medicine, ed.

2, New York, Oxford University Press, 1969.

Medical Council of the U.K.: Aids to the Examination of the Peripheral

Nervous System, Palo Alto, Calif., Pendragon House, 1978.

Monrad-Krohn, G.H., Refsum, S.: The Clinical Examination of the

Nervous System, ed. 12, London, H.K. Lewis & Co., 1964.

Wolf, J.K.: Segmental Neurology, A Guide to the Examination and

Interpretation of Sensory and Motor Function, Baltimore, University

Park Press, 1981.

Questions

Define the following terms:

spasticity, rigidity, hemiparesis/plegia, bradykinesia,

paraparesis/plegia, upper motor neurons, lower motor neurons,

internal capsule, chorea, athetosis, dystonia, hemiballism, tic,

fasciculation.

Spasticity is a resistance to passive movements that is greatest at the initiation of motion

(particularly of a rapid movement). It is often a sign of overactive muscle stretch reflexes.

Hemiparesis/plegia paralysis or paresis (weakness) of one side of the body.

Rigidity is a smooth resistance to passive movement that occurs throughout the range of

motion and usually results from extrapyramidal disorders such as Parkinson's disease.

Bradykinesia is a pathological slowing of motor performance often seen with Parkinson's

disease and parkinsonism.

Paraparesis/plegia paralysis or paresis of both lower extremities.

Upper motor neurons are the principal descending motor pathways for voluntary

movement, including the corticospinal and corticobulbar tracts (and some other

associated tracts).

Lower motor neurons are the anterior horn motor neurons and their axons that extend

through the ventral nerve root and the peripheral nerves to reach the neuromuscular

junction.

The internal capsule is the primary locus through which the upper motor neuron

(corticospinal and corticobulbar) pathways descend.

Chorea a purposeless, involuntary, random twitching movement.

Athetosis a purposeless, involuntary writhing movement.

Dystonia is an involuntary, sustained twisting position of the body or a body part

(torticollis, for example, when it involves the head).

Hemiballism a repeated, involuntary, flinging or flipping movement of a part of the body

on one side, usually due to damage to the subthalamic nucleus.

Tic is a rapid movement, tending to be repeated in the same pattern over and over.

Fasciculation an involuntary twitching of individual motor units, usually visible as a

rippling of the skin but usually not resulting in any actual movement of the body part.

10-1. Describe the course of "upper motor neurons".

Answer 10-1. Upper motor neurons (coticospinal and corticobulbar tracts) arise in the

motor cortex, traverse the internal capsule, cerebral peduncle and pyramids of the brain

stem.

10-2. Over what functions do the upper motor neurons exert the greatest

control (what movements are most effected by damage)?

Answer 10-2. They are mostly involved in control of distal movements (such as hand and

fingers). Proximal functions (such as shoulder shrug) have bilateral control.

10-3. Where are sites of potential lesion producing lower motor neurons

signs and symptoms?

Answer 10-3. Lower motor neuron damage can be anywhere along the pathway from the

anterior horn motor neuron, ventral root, plexus or peripheral nerve.

10-4. What are the features of lower motor neuron damage?

Answer 10-4. Lower motor neuron damage results in decreased reflex and usually

atrophy. It may also produce fasciculations.

10-5. What is the significance of fasciculations?

Answer 10-5. Diffuse, persistent and extensive fasciculations suggests motor neuron

disease or damage (transient fasciculations are common and benign if unaccompanied by

weakness or reflex change).

10-6. What are the characteristics of peripheral nerve damage?

Answer 10-6. Effects of nerve damage are most often seen distally, reflexes are affected

early and atrophy is often present.

10-7. What are the characteristics of muscle disease?

Answer 10-7. Symptoms are usually most evident proximally, there is no sensory loss,

reflexes only affected late and atrophy is not severe.

10-8. What are the characteristics of basal ganglia disease?

Answer 10-8. Muscle tone, postures, and patterned movements are most affected.

Parkinsonism is common, with bradykinesia, difficulty initiating movements, delayed

postural reflex responses and rigidity. Abnormal movements at rest are common: resting

tremor, chorea, athetosis, dystonia, hemiballism.

10-9. What are the characteristics of cerebellar disease?