3Motor Testing

8/7/2019 3Motor Testing

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THE NEUROLOGIC EXAMINATIONMOTOR SYSTEM EXAMINATIONMOTOR SYSTEM EXAMINATION


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Motor System Examination, including Cerebellar tests

Inspection: Body position

Involuntary movements

Muscle bulk

Muscle Tone

Manual Motor Testing

Coordination and Gait


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Area for Hand Skills. In the premotor area immediately

anterior to the primary motor cortex for the hands and

fingers is a region neurosurgeons have identified as

important for hand skills. That is, when tumors or

other lesions cause destruction in this area, hand

movements become uncoordinated and nonpurposeful,

a condition called motor apraxia (see below).

Guyton pp 687,11th ed


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Transmission of Signals from the

Motor Cortex to the Muscles

Motor signals are transmitted directly from the cortex

to the spinal cord through the corticospinal tract and

indirectly through multiple accessory pathways that

involve the basal ganglia, cerebellum, and various

nuclei of the brain stem. In general, the direct pathways

are concerned more with discrete and detailed movements,

especially of the distal segments of the limbs,

particularly the hands and fingers.


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The most important output pathway from the motor cortex is the

corticospinal tract, also called the pyramidal tract, shown in Figure

554.The corticospinal tractoriginates about 30 per cent from the

primary motor cortex, 30 per cent from the premotor andsupplementary motor areas, and 40 per cent from the

somatosensory areas posterior to the central sulcus. After leaving

the cortex, it passes through the posterior limb of the internal

capsule (between the caudate nucleus and the putamen of the basal

ganglia) and then downward through the brain stem, forming

thepyramids of the medulla. The majority of thepyramidal fibers then cross in the lower medulla to the

opposite side and descend into the lateralcorticospinal

tracts of the cord, finally terminating principally on the

interneurons in the intermediate regions of the cord

gray matter; a few terminate on sensory relay neuronsin the dorsal horn, and a very few terminate directly

on the anterior motor neurons that cause muscle

contraction.


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A few of the fibers do not cross to the opposite side

in the medulla but pass ipsilaterally down the cord in

the ventralcorticospinal tracts. Many if not most of

these fibers eventually cross to the opposite side of the

cord either in the neck or in the upper thoracic region.These fibers may be concerned with control of bilateral

postural movements by the supplementary motor

cortex.

The most impressive fibers in the pyramidal tract are

a population of large myelinated fibers with a mean

diameter of 16 micrometers. These fibers originate

from giant pyramidalcells, called Betzcells, that are

found only in the primary motor cortex.The Betz cells

are about 60 micrometers in diameter, and their fibers

transmit nerve impulses to the spinal cord at a velocity

of about 70 m/sec, the most rapid rate of transmissionof any signals from the brain to the cord. There

are about 34,000 of these large Betz cell fibers in each

corticospinal tract. The total number of fibers in each

corticospinal tract is more than 1 million


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Examination of the motor system

1. Inspection and Palpation

A. Tremors: Parkinsonian / Metabolic / Cerebellar / EssentialRubral / Physiologic tremor, Tremor of Hepatic

encephalopathy

B. Dystonia

C. Involuntary movements: Chorea, Tardive dyskenisia,

Athetosis, Pseudoathetosis, Choreoathetosis, Ballism

D. Clonus / MyoclonusE. Spasm: muscle cramps, oculogyric crisis, hemifacial

cramps, palatal myoclonus or nystagmus,

blepharospasm, hiccup

F. Seizures

2. Muscle SymmetryLeft to Right

Proximal vs. Distal

Atrophy (particular attention to the hands, shoulders, and thighs)

3. Gait


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Examination of the motor system

Muscle Tone

Ask the patient to relax.

Flex and extend the patient's fingers, wrist, and elbow.

Flex and extend patient's ankle and knee.There is normally a small, continuous resistance to passive

movement.

Observe for decreased (flaccid) or increased (rigid/spastic)

tone.


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Testing of motor and sensory function requires a basic understanding of

normal anatomy and physiology.

In brief:

Voluntary movement begins with an impulse generated by cell bodies

located in the brain.

Signals travel from these cells down their respective axons, forming the

Corticospinal (a.k.a. Pyramidal) tract.

At the level of the brain stem, this motor pathway crosses over to theopposite side of the body and continue downward on that side of the

spinal cord. The nerves which comprise this motor pathway are

collectively referred to as Upper Motor Neurons (UMNs).

At a specific point in the spinal cord the axon synapses with a 2nd

nerve, referred to as a Lower Motor Neuron (LMN). The precise locationof the synapse depends upon where the lower motor neuron is destined

to travel. If, for example, the LMN terminates in the hand, the synapse

occurs in the cervical spine (i.e. neck area). However, if its headed for

the foot, the synapse occurs in the lumbar spine (i.e. lower back).


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The UMNs are part of the Central Nervous System (CNS), which is

composed of neurons whose cell bodies are located in the brain or spinal

cord.

The LMNs are part of the Peripheral Nervous System (PNS), made

up of motor and sensory neurons with cell bodies located outside of the

brain and spinal cord. The axons of the PNS travel to and from the

periphery, connecting the organs of action (e.g. muscles, sensory

receptors) with the CNS. Nerves which carry impulses away from the CNS are referred to

Efferents (i.e. motor) while those that bring signals back are called

Afferents (i.e. sensory).

Axons that exit and enter the spine at any given level generally

connect to the same distal anatomic area. These bundles of axons,

referred to as spinal nerve roots, contain both afferent and efferent

nerves. The roots exit/enter the spinal cord through neuroforamina in the

spine, paired openings that allow for their passage out of the bony

protection provided by the vertebral column.


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As the efferent neurons travels peripherally, components from

different roots commingle and branch, following a highly programmedpattern. Ultimately, contributions from several roots may combine to

form a named peripheral nerve, which then follows a precise anatomic

route on its way to innervating a specific muscle.

The Radial Nerve, for example, travels around the Humerus

contains contributions from Cervical Nerve Roots 6, 7 and 8 andinnervates muscles that extend the wrist and supinate the forearm.

It may help to think of a nerve root as an electrical cable composed

of many different colored wires, each wire representing an axon. As

the cable moves away from the spinal cord, wires split off and head to

different destinations. Prior to reaching their targets, they combine with

wires originating from other cables. The group of wires that ultimatelyends at a target muscle group may therefore have contributions from

several different roots.


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SIGN UNM Lesion LMN Lesion

Weakness Yes Yes

Atrophy No * Yes

Fasciculation No Yes

Reflexes Increased Decreased

Tone Increased Decreased

*Mild atrophy may develop due to disuse

Signs ofUpper Motor Neuron (UMN) and Lower

Motor Neuron (LMN) Lesions


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Motor Testing

The muscle is the unit of action that causes movement.Normal motor function depends on intact upper andlower motor neurons, sensory pathways and input from anumber of other neurological systems. Disorders ofmovement can be caused by problems at any pointwithin this interconnected system.

Muscle Bulk and Appearance:

This assessment is somewhat subjective and quitedependent on the age, sex and the activity/fitness levelof the individual. A frail elderly person, for example, willhave less muscle bulk then a 25 year old body builder.With experience, you will get a sense of the normalrange for given age groups, factoring in their particularactivity levels and overall states of health.


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Motor Testing

Things to look for:Using your eyes and hands, carefully examine the major

muscle groups of the upper and lower extremities. Palpation of the

muscles will give you a sense of underlying mass. The largest and

most powerful groups are those of the quadriceps and hamstrings

of the upper leg (i.e. front and back of the thighs). The patientshould be in a gown so that the areas of interest are exposed.

Muscle groups should appear symmetrically developed when

compared with their counterparts on the other side of the

body. They should also be appropriately developed, after makingallowances for the patients age, sex, and activity level.


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Muscle Assymetry

While both legs have well developed musculature,

the left has greater bulk.


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Motor Testing

There should be no muscle movement when the limb is at rest.

Rare disorders (e.g. Amyotrophic Lateral Sclerosis) result in

death of the lower motor neuron and subsequent denervation of

the muscle. This causes twitching of the fibers known as

fasciculations, which can be seen on gross inspection of affected

muscles.

Tremors are a specific type of continuous, involuntary muscle

activity that results in limb movement. Parkinsons Disease (PD),

for example, can cause a very characteristic resting tremor of the

hand (the head and other body parts can also be affected) that

diminishes when the patient voluntarily moves the affected limb.

Benign Essential Tremor, on the other hand, persists throughout

movement and is not associated with any other neurological

findings, easily distinguishing it from PD.


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Motor Testing

The major muscle groups to be palpated include:

biceps, triceps, deltoids, quadriceps and hamstrings.

Palpation should not elicit pain. Interestingly, myositis (a

rare condition characterized by idiopathic muscle

inflammation) causes the patient to experience weakness

but not pain.


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If there is asymmetry, note if it follows a particular pattern.

Remember that some allowance must be made for handedness(i.e. right v left hand dominance).

Does the asymmetry follow a particular nerve distribution,suggesting a peripheral motor neuron injury? For example,muscles which lose their LMN innervation become very atrophic.

Is the bulk in the upper and lower extremities similar? Spinalcord transection at the Thoracic level will cause upper extremitymuscle bulk to be normal or even increased due to increaseddependence on arms for activity, mobility, etc. However, themuscles of the lower extremity will atrophy due to loss of

innervation and subsequent disuse.

Is there another process (suggested by history or otheraspects of the exam) that has resulted in limited movement of aparticular limb? For example, a broken leg that has recentlybeen liberated from a cast will appear markedly atrophic.

Motor Testing


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Diffuse Muscle Wasting:

Note loss muscle bulk in left hand due to peripheral denervation.

In particular, compare left and right thenar eminences.


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MOTOR TESTING: Tone

When a muscle group is relaxed, the examiner should be able to

easily manipulate the joint through its normal range of motion. This

movement should feel fluid. A number of disease states may alter this

sensation. For the screening examination, it is reasonable to limit this

assessment to only the major joints, including: wrist, elbow, shoulder, hips

and knees.

Technique:

Ask the patient to relax the joint that is to be tested.

Carefully move the limb through its normal range of motion, being careful

not to maneuver it in any way that is uncomfortable or generates pain. Be

aware that many patients, particularly the elderly, often have other medical

conditions that limit joint movement. Degenerative joint disease of theknee, for example, might cause limited range of motion, though tone

should still be normal.

If the patient has recently injured the area or are in pain, do not perform

this aspect of the exam.


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Disorders that do not directly affect the muscles, upper or lower

motor neurons can still alter tone.

Perhaps the most common of these is Parkinsons Disease (PD).

This is a disorder of the Extra Pyramidal System (EPS). The

EPS normally contributes to initiation and smoothness ofmovement. PD causes increased tone, generating a ratchet-like

sensation (known as cog wheeling) when the affected limbs are

passively moved by the examiner.

MOTOR TESTING: Tone


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MOTOR TESTING: Strength

As with muscle bulk, strength testing must take into account the

age, sex and fitness level of the patient. For example, a frail,

elderly, bed bound patient may have muscle weakness due to

severe deconditioning and not to intrinsic neurological disease.

Interpretation must also consider the expected strength of the

muscle group being tested. The quadriceps group, for example,

should be much more powerful then the Biceps.


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Proximal

weakness Suggestive of myopathy

Distal

Weakness

Suggestive of peripheral

neuropathy

Pyramidal

Weakness

Suggestive of UMN

dysfunction


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Grading of Muscle Strength

Grade Description

0/5 No muscle movement

1/5 Slight contractility but no joint motion

2/5 Movement at the joint, but not against gravity

3/5 Movement against gravity, but not against added

resistance

4/5 Movement against resistance, but less than

normal

5/5 Normal strength


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Muscle strength is traditionally graded

using the following scale:

HARISSONS 0 = no movement

1 = flicker or trace of contraction but no associated movement at a

joint

2 = movement with gravity eliminated 3 = movement against gravity but not against resistance

4 = movement against a mild degree of resistance

4 = movement against moderate resistance

4+ = movement against strong resistance

5 = full power


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However, in many cases it is more practical to

use the following terms (HARISSONS-Part16

chap 361 17 ed):

Paralysis = no movement

Severe weakness = movement with

gravity eliminated

Moderate weakness = movement against

gravity but not against mild resistance

Mild weakness = movement againstmoderate resistance

Full strength


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Specifics of Strength Testing - Major Muscle Groups: In thescreening examination, it is reasonable to check only the majormuscles/muscle groups. More detailed testing can be performedin the setting of discrete/unexplained weakness. The names ofthe major muscles/muscle groups along with the spinal roots andperipheral nerves that provide their innervation are provided

below. Nerve roots providing the greatest contribution are printedin bold. More extensive descriptions of individual muscles andtheir functions, along with their precise innervations can be foundin a Neurology reference text.

Intrinsic muscles of the hand (C 8, T 1): Ask the patient to spreadtheir fingers apart against resistance (abduction). Then squeeze

them together, with your fingers placed in between each of theirdigits (adduction). Test each hand separately. The muscles whichcontrol adduction and abduction of the fingers are called theInterossei, innervated by the Ulnar Nerve.

MOTOR TESTING: Strength


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Intrinsic muscles of the hand (C 8, T 1)

Ask the patient to spread their fingers apart against resistance

Squeeze them together, with your fingers placed in between each of

their digits (adduction). Test each hand separately.The muscles which control adduction and abduction of the fingers are

called the Interossei, innervated by the Ulnar Nerve.


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Flexors of the fingers (C 7, 8, T1)

Ask the patient to make a fist, squeezing their hand around two of your

fingers. If the grip is normal, you will not be able to pull your fingers out.

Test each hand separately.The Flexor Digitorum Profundus controls finger flexion and is innervated by

the Median (radial ) and Ulnar (medial ) Nerves.


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Wrist flexion (C 7, 8, T 1)

Have the patient try to flex their wrist as you provide resistance. Test

each hand separately.

The muscle groups which control flexion are innervated by the Medianand Ulnar Nerves.


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Elbow Flexion (C 5, 6)

Have the patient bend their elbow to ninety degrees while keeping their

palm directed upwards. Then direct them to flex their forearm while you

provide resistance.The main flexor (and supinator) of the forearm is the Brachialis Muscle

(along with the Biceps Muscle). These muscles are innervated by the

Musculocutaneous Nerve


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Shoulder Adduction (C5 thru T1)

Have the patient flex at the elbow while the arm is held out from the

body at forty-five degrees. Then provide resistance as they try to further

adduct at the shoulder.The main muscle of adduction is the Pectoralis Major, though the

Latissiumus and others contribute as well.


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Shoulder Abduction (C 5, 6)

Have the patient flex at the elbow while the arms is held out from the

body at forty-five degress. Then provide resistance as they try to further

abduct at the shoulder.The deltoid muscle, innervated by the axillary nerve, is the main muscle

of abduction.


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Hip Flexion (L 2, 3, 4)

With the patient seated, place your hand on top of one thigh and

instruct the patient to lift the leg up from the table.

The main hip flexor is the Iliopsoas muscle, innervated by the femoralnerve.


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Hip Abduction (L 4, 5, S1)

Place your hands on the outside of either thigh and direct the patient

to separate their legs against resistance.

This movement is mediated by a number of muscles.


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Hip Adduction (L2, 3, 4)

Place your hands on the inner aspects of the thighs.

A number of muscles are responsible for adduction. They are

innervated by the obturator nerve


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Knee flexion (L5, S1, 2)

Have the patient rest prone. Then have them pull their heel up and off

the table against resistance.

Flexion is mediated by the hamstring muscle group, via branches of thesciatic nerve.


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Ankle Dorsiflexion (L4, 5)

Direct the patient to pull their toes upwards while you provide

resistance with your hand.

The muscles which mediate dorsiflexion are innervated by the deep

peroneal nerve. The peroneal nerve is susceptible to injury at the point

where it crosses the head of the fibula (laterally, below the knee). If

injured, the patient develops Foot Drop, an inability to dorsiflex the

foot.


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Ankle PlantarFlexion (S 1, S 2)

Have the patient step on the gas while you provide resistance.

The gastrocnemius and soleus, the muscles which mediate this

movement, are innervated by a branch of the sciatic nerve. Plantarflexion and dorsiflexion can also be assessed by asking the patient to

walk on their toes (plantar flexion) and heels (dorsiflexion).


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It is generally quite helpful to directly compare right vs left

sided strength, as they should more or less be equivalent(taking into account the handedness of the patient). If there

is weakness, try to identify a pattern, which might provide a

clue as to the etiology of the observed decrease in strength.

In particular, make note of differences between:

Right vs Left Proximal muscles vs distal

Upper extremities vs lower

Or is the weakness generalized, suggestive of a systemic

neurological disorder or global deconditioning


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Common peripheral nerves, territories of innervation, and clinical

correlates.

Peripheral Nerve SensoryInnervation

Motor Innervation ContributingSpinalNerve Roots

Clinical

Radial Nerve Back of thumb,index, middle, and ring finger; back of

forearm

Wrist extension andabduction of thumb inpalmer plane

C6, 7, 8 At risk for compression athumerus, known as

"Saturday Night Palsy

Ulnar Nerve Palmar and dorsalaspects of pinky and of ring finger

Abduction of fingers(intrinsic muscles ofhand)

C7, 8 and T1 At risk for injury withelbow fracture.

Can get transientsymptoms when inside of

elbow is struck ("funny

bone" distribution)

Median Nerve Palmar aspect of thethumb, index, middleand ring finger;palm below thesefingers.

Abduction of thumbperpendicular to palm(thenar muscles).

C8, T1 Compression at carpaltunnel causes carpal

tunnel syndrome

Lateral CutaneousNerve of Thigh

.Lateral aspect thigh L1, 2 Can become compressedin obese patients, causing

numbness over its

distribution

Peroneal Lateral leg, top of foot

Dorsiflexion of foot(tibialis anteriormuscle)

L4, 5; S1 Can be injured withproximal fibula fracture,

leading to foot drop

(inability to dorsiflex foot)


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Neurologic examinationGAIT & STATION


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Cerebellar ataxia is not ameliorated by visual orientation

Have the patient stand in one place. This is a test ofbalance, incorporating input from the visual, cerebellar,proprioceptive, and vestibular systems. If they are able

to do this, have them close their eyes, removing visualinput. This is referred to as the Romberg test. Loss ofbalance suggests impaired proprioception.

In disease of the cerebellum:

- lateral lobe, falling is toward the affected side

- frontal lobe, falling is to the opposite side

- midline or vermis, falling indiscriminately

TESTING OF STATION

(EQUILIBRATORY COORDINATION)


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Ask the patient to stand from a chair, walk across theroom, turn, and come back towards you. Pay particularattention to:

Difficulty getting up from a chair: Can the patient easily arisefrom a sitting position? Problems with this activity might suggestproximal muscle weakness, a balance problem, or difficultyinitiating movements.

Balance: Do they veer off to one side or the other as might occurwith cerebellar dysfunction? Disorders affecting the leftcerebellar hemisphere (as might occur with a stroke or tumor)will cause patients to fall to the left. Right sided lesions willcause the patient to fall to the right. Diffuse disease affectingboth cerebellar hemispheres will cause a generalized loss ofbalance.

Rate of walking: Do they start off slow and then accelerate,perhaps losing control of their balance or speed (e.g. as might

occur with Parkinsons Disease)? Are they simply slow movingsecondary to pain/limited range of motion in their joints, as mightoccur with degenerative joint disease? etc.

Attitude of Arms and Legs: How do they hold their arms andlegs? Is there loss of movement and evidence of contractures(e.g. as might occur after a stroke)?


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Heel to Toe Walking: Ask the patient to walk in a

straight line, putting the heel of one foot directly

in front of the toe of the other. This is referred to

as tandem gait and is a test of balance. Realizethat this may be difficult for older patients (due to

the frequent coexistence of other medical

conditions) even in the absence of neurological

disease.


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Normal posture, step size,

and arm swing

Tandem Walking


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Steppage Gait Retropulsion


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CEREBELLAR TESTING

The cerebellum fine tunes motor activity and assists withbalance. Dysfunction results in a loss of coordination andproblems with gait. The left cerebellar hemispherecontrols the left side of the body and vice versa.

Specifics of Testing: There are several ways of testingcerebellar function. For the screening exam, using onemodality will suffice. If an abnormality is suspected oridentified, multiple tests should be done to determinewhether the finding is durable. That is, if the abnormality

on one test is truly due to cerebellar dysfunction, othertests should identify the same problem. Gait testing, animportant part of the cerebellar exam.


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Rapid Alternating Hand Movements: Direct the patient to touch first the palm and then the dorsal side of

one hand repeatedly against their thigh.

Then test the other hand.

Interpretation: The movement should be performed with speedand accuracy. Inability to do this, known as dysdiadokinesia, maybe indicative of cerebellar disease.

Heel to Shin Testing: Direct the patient to move the heel of one foot up and down along the

top of the other shin.

Then test the other foot.

Interpretation: The movement should trace a straight line along

the top of the shin and be done with reasonable speed.

CEREBELLAR TESTING


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Heal Shin Test


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The Romberg test. Have the patient stand still with heels and

toes together. Ask the patient to close her eyes and balance

herself. If the patient loses her balance, the test is positive.


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