Clinical neuroanatomy for CT1s

Dr John O’DonovanFriday 8th June

Firstly

Secondly

Thirdly

Basics

• Neurons of which there are many types, with many functions, make up the nervous system.

• The nervous system for our purposes comprises the brain, spinal cord and peripheral nerves.

• Focus for CT1 should be on both clinical and scientific but more so on clinical.

• The anatomy tends to be bottom up but clinical signs tend to be top down.

The brainin the skull Frontal lobes Temporal lobes Occipital lobes Parietal lobes Limbic lobe/system CerebellumPituitary and hypothalamus (hypophysis)Pons, midbrain, medulla oblongata-cranial nerves and nuclei.

Frontal lobe

Match them UP? Look at the size of that frontal lobe!

Frontal lobe syndromes

• Orbitofrontal: disinhibition, witzelsucht, euphoria, lability, poor judgment and poor attention.

• Frontal convexity: apathetic, indifferent, retarded, perseverating

• Medical frontal: akinetic, mutism, gait problems and incontinence.

• Massive frontal lobe syndromes: combination of all four.

• All a gross oversimplification.

Worth noting the following about cortical lesions

• Less deficit per volume affected• Frequently patients are unaware of extent of deficit, “anosagnosia”• Tends to be inconsistent• Multimodal deficits eg alexia, need analysis. • There is individual variation in cortical function. • The neurology is syndrome based and therefore these are by definition

imprecise to some extent• Clinical presentation also varies by tempo and nature of damage• Cortical plasticity means that elementary functions improve better then

complex deficits.• Cortex is susceptible to global systemic fluctuation, such as delirium• Selective cortical lesions tend to cause seizures and multimodal deficits

Other signs

• Precentral gyrus: face, hand, leg and urinary incontinence if bilateral. Also with unilateral if massive.

• Mesial aspect: akinesis, perseveration, grasping, “salutatory seizures”, alien hand sign, transcortical motor aphasia, bilateral ideomotor apraxia

• Lateral aspect: impaired saccades, pure agraphia in dominant hemisphere, contralateral, arm weakness

• Frontal pole: orbitofrontal as before degree of acquired sociopathy

Frontal lobe summary

Motor problems• Eye movements on

contralateral side • Contralateral hemiparesis,

face, hand, leg (arm more then leg)

• Inability to start or stop correctly, akinesis and perseveration

• Oddities, alien hand, grasping and pure agraphia

Non motor problems• Motor aphasia: Broca’s • Incontinence if bilateral • Inability to plan ahead• Poor self monitoring and

social judgment• Acquired sociopathy • Dysexecutive

• Remember caveat about cortical lesions.

Temporal lobes

Lateral aspect Remember the hippocampus

Temporal lobe

Lanuage• Wernicke’s area, receptive

aphasia

Non language funcions • Emotion • Memory by means of the

hippocampal complex• Verbal memory is more left

based and visual is more right based. (simplification)

• Complex partial seizures NB

Temporal lobe 2

Inferomedial• Anmesia • Bilateral anterior temporal

lobe lesions can lead to Kluver-Bucy Syndrome with visual agnosia, hyperoral, tameness, hypersexual, hypomotile and hypermetamorphosis (paying attention to every visual stimulus)

Lateroinferior• Dominant: transcortical

sensory aphasia and word selection anomia, in essence receptive aphasias

• Non Dominant: Impaired recognition of facial emotional expression.

Temporal lobe 2

Laterosuperior • Dominant: pure word

deafness and sensory aphasia.

• Nondominant: sensory amusia and sensory aprosodia.

Bilateral lesions of lateral superior aspect

• Auditory agnosia

Temporal lobe 3

Eye problems• Contralateral superior

quadrantic anopsia, Meyer’s loop etc.

• Seizures• Temporal lobe both left and right,

hippocampus, amygdala and connections are frequent source of complex partial seizures-separate discussion.

Non localising signs• Auditory hallucinations • Complex visual

hallucinations

Parietal Lobe

Sensory input Making sense of it all

Parietal lobe 1

Post central gyrus• damage causes

contralateral sensory disturbance, pain and paresthesia

• Mesial aspect in dominant hemisphere can cause transcortical sensory aphasia

Lateral aspect• Dominant, parietal apraxia,

finger agnosia, acalculia, right left disorientation, literal alexia and possibly conduction aphasia. Note Gerstman Syndrome

• Non Dominant, anosognosia, autopagnosia, spatial disorientation, hemispatial neglect, constructional and dressing apraxia

To simplify

• Parietal lobes are sensory and put sensory input into context.

• Dominant lobe injury on lateral aspect can allegedly cause a Gerstman Syndrome. This is a bit of a myth, but a useful one for the MRCPsych.

Gerstman Syndrome

• Agraphia –can’t read. • Acalculia – can’t do arithmetic.• Finger agnosia –can’t recognize fingers.• Left right disorientation – left verus right• Dominant angular and marginal gyrus.

• Very debatable if it exists, beloved of post graduate examinations.

Occipital Lobes

Occipital lobe

Mesial • Visual field cut • Visual agnosia • Visual hallucinations• Anton syndrome-cortical

blindness without insight into blindness (anosagnosia)

• Alexia without agraphia-generally also with splenium involvment.

Lateral• Alexia with agraphia • Impaired optokinetic

nystagmus• Impaired scanning.

To simplify

John’s simple rules

• Frontal lobe is ultimately about doing stuff, speaking, walking, planning, studying etc.

• Temporal lobe all about memory and understanding language. Obviously the receptive language area is beside the ears!, memory is a bilateral function, anything you hear or how you hear it.

• Parietal lobe is ultimately about sensory input• Occipital lobe is about vision• Left hemisphere is dominant, any question with

language, check dominance.

MCQs Frontal lobes

Frontal lobe lesions cause• Contralateral sensory

problems. • Transcortical sensory

aphasia• Incontinence• Witzelsucht• Reckless behavior• Versive seizures• Alien hand phenomena

Frontal lobe lesions 2• Being rude to in laws • Watching TV all night • Perseveration• Grasping • Primitive reflexes • Echopraxia • Echolalia• Pure agraphia• Problems with memory

MCQs Temporal lobes

Bilateral temporal lobe lesions cause

• Disorders of memory • Transcortical motor aphasia • Amnesia • Paraamnestic phenomena• Incontinence • Contralateral motor

weakness• May if bilateral cause Kluver-

Bucy Syndrome• Emotional problems

Dominant temporal lobe lesions cause

• Inferior visual quadrantopia• Auditory agnosia • Amusia • Aprosody• Difficulty recognizing when

your wife is angry• Hallucinations?

MCQs Parietal lobes

Parietal lobe lesions cause• Motor problems • Dressing apraxia• Anosagnosia • Autopagnosia • Alexia• Finger agnosia• Visual integration problems

Dominant parietal lesions always

• Cause Gerstman Syndrome• Contralateral paresthesia • Reduced light touch, but

preserved propioception on contralteral side.

• Acalculia • Cause hemispatial neglect.

story• The four lobes of the brain were friends. • Frontal Frank was a leader. He decided what to do and how to do it. He was always talking

and always moving around. He made all the decisions and was a dominant personality. Tempermental Tim on the other hand, was always listening out for what anybody said about him and he had a prodigious memory but was prone to being moody and sometimes would seize up with odd feelings, which he could not explain very well. Frank used to go out with Pretty Parie but he broke up after being unable to satisfy her sensory needs. On top of which, despite dominating Frank, she did not read, add up, know her left from right or ever recognize her fingers and he found it hard to deal with her constant whining about her right side not being properly dressed and neglecting him all the time. Ultimately he went to tempermental Tim for advice who told him to speak with Occy who had a reputation as a bit of a visionary. Occy told Frank that he couldn’t see what was in it for him and to have a bit of a look around on the other side. Frank never took advice well and ended up beating Occy half blind, but suffered a stroke affecting his arm in particular and ended up mute and incontinent. This upset Tim so badly that he went into status epilpticus and lost his memory for everything. Pretty Parie meanwhile continued trying to make sense of it all.

Occipital lobe lesions

If dominant• Cause ipsilateral

hemianopsia • Can cause colour

desaturation.• Can cause alexia• Mean that you can no

longer drive• May cause visual

hallucinations

If bilateral• Can cause cortical blindness• Are normally caused by

pump failure. • Can occur in prion disease• Impair the pupil response• Can cause Balint Syndrome

And now for something different

• Neuroanatomy of vision• Neuroanatomy of the spinal cord• Neuroanatomy of the basal ganglia and

cerebellum• Neuroanatomy of the peripheral nerves

Diagnosis?

Diagnosis

Diagnosis

Pupils 4 parts

Optic nerve-pretectal area in midbrain

Pretectum to Edwinger Westphal nucleus (parasympathetic nucleus of !!! Occulomotor nerve)

Edwinger Westphal nucleus bilateral to ciliary ganglion

Ciliary ganglion to constrictor muscles of iris

Light near dissociationArgyll Robertson Pupil, syphilitic eye disease, very rare, lesion site around the aqueduct. “the prostitute accomodates but does not react”

Holmes-Adie tonic pupilWith arreflexia Adie Syndrome, prevalence is 1:500, degeneration of ciliary ganglion, other name is tonic pupil.

Parinaud Syndrome, rostral midbrain stroke, presumably from damage to midbrain

Remember 80% of the ciliary ganglion response is for accomodation, not light.

Dilated pupil from occulomotor palsy-occulomotor nerve, ptosis, down and out with mydriasis.

Remember parasympathetic fibres run on the outside of the nerve and are susceptible to trauma.

Coning of the brain, trauma, ptuitary lesions, PICA aneurysms.

Axonal palsies from diabetes and vasculitis tends to be pupil sparing.

Drugs that cause mydriasis

Atropine Hyoscine Scopolamine TropicamideAll anti cholinergics

Anti cholinergics-not drugs with weak anti cholinergic effects.

Horner’s Syndrome

Horner’s Syndrome

• Congenital • Anywhere in sympathetic chain• Hypothalamus • C8/T1 root• Pancoast tumours, apex of lung

Visual pathways

Visual pathways 2

• Tends not to be asked. • Generally very basic, remember to draw the

pathway. • Pituitary lesions cause bitemporal

hemianopsia • Occipital cause a contralateral field cut, left

occipital lesions cause right sided hemianopsia.

MS eye signs, optic neuritis and internculear opthalmoplegia (dissociated nystagmus)

Eye MCQs

a normal pupil response• Daylight causes mydriasis• Both pupils are equal in size• Both respond consensually• Two cranial nerves are used• Second relay centre is in the

pons• The ciliary ganglion is

sympathetic• Accomodation is to light as

2:1

Argyll Robertson pupils• Are always pathological• Can be associated with an

absent ciliospinal reflex• Don’t react to light• React quickly to

accomodation• Are common with HIV

infection• Are similar to Holmes-Adie

pupils

Eye MCQs

Match the following• Growing hands, feet and

diabetes• Young woman with weak

left leg and double vision• Smoker with a painful

armpit• Cortical blindness• Xanthochromia

Possible answers• Compressive third nerve

palsy.• Bitemporal hemianopsia • Horner’s Syndrome • Old variant CJD • Multiple sclerosis• Myasthenia gravis • Relative afferent pupil

defect.

Spinal cord and brainstem

Brainstem

Brainstem

• Use cranial nerve nuclei to find lesion level. • Remember deccusation in the pyramids of the

medulla oblongata-crossed syndromes.• Lateral medullary syndrome frequently sneaks

in and therefore must be known. • Remember pons-trigeminal nerve, pontine

pupils, CPM-central pontine myelinosis• Unlikely to be asked specifics

Cranial nerves

Spinal cord pathways

Corticospinal tract Spinothalamic

Spinal cord

Posterior columns Syringomyelia

Syringomyelia/BulbiaHole in central spinal cord filled by CSF

Results in weakness-combined lower and upper motor neuron signs

Dissociated sensory loss-meaning that it affects spinothalamic tracts with anaesthesia and absence of temperature perception.

Can result in Charcot Joints, most commonly in hands and shoulders

Classically shows a cape distribution sensory loss

Syringobulbia is when it extends into the bulbar area and causes cranial nerve and brainstem signs. Norallly lower cranial nerves and sometimes trigeminal.

Brown-Sequard SyndromeHemitransection of cord Same side as lesion UMN weakness and posterior column problems

Contralateral side loss of pain and temperature (spinothalamic)

Cord transectionRarely asked as questionIn general, below lesion spasticity and weakness

Plantar externsor and clonus

Neurogenic bladder and bowel

Lesion level guides disability

Cord level does not equate precisely to root level

Peripheral nerves

• Highly unlikely to be asked as a question. • Some basics- peripheral nerve lesions or lower

motor neruon lesions cause arreflexia at level of lesion, atrophy, weakness and fasiculations.

• Can be subdivided into many types of lesion but simply put, either axonal or demyelinating such as AIDP.

• Axonal lesions tend to occur in vascular process and cause more gross atrophy.

Peripheral neuropathies

causes Peripheral nerves

Peripheral neuropathy

• Glove and stocking • Longest nerves first (sciatic!), begins in feet. • Common causes of painful peripheral

neuropathy diabetes and drink, B12. • Commonest cause of peripheral neuropathy

worldwide is leprosy. • Acute flacid weakness-AIDP, GBS

MCQs on cranial nerves, spinal cord and peripheral nerves

• Bells palsy is a lesion of the trigeminal nerve.

• The afferent arc of the corneal reflex is in the maxillay branch of the trigeminal nerve

• Swallowing requires an intact hypoglossal nerve

• Bilateral LMN facial palsies can occur in sarcoid

• Brown Sequard syndrome results in ipsilateral spinothalamic function loss

• UMN lesions cause fasiculations • A syrinx of the thoracic cord can

cause bladder problems

• Following cause peripheral neuropathy

• Lead • Diabetes • Acute intermittent

porphyria• Metronidazole • Alcohol • B12 deficiency • Cryoglobulinaemia • Lithium

Cerebellum and basal ganglia

Basal ganglia and cerebellum

• Functions are ultimately to provide smooth and effective movements.

• Much greater role then simply movement, needed for cognition, emotion, reward networks, executive functioning.

• Multiple feedback loops between cortex and basal ganglia, allows cortex and basal ganglia to self monitor, to some extent.

Cerebellar SignsIpsilateral Ataxia Rebound Slow reflexes Nystagmus Tremor Difficulty with rapidly pronating/supinating movements-dysdiadokinesiDysarthria Hypotonia

Midline-vermian commonly from alcohol Central ataxia Dysarthria

Causes of cerebellar disease

• Alcohol • Drugs-intoxication eg phenytoin toxicity• Toxins • Hypoxia • Stroke • Trauma• Celiac disease • Paraneoplastic with breast/ovarian in particular• Congenital-SCAs, pure cerebellar degenerations• Congenital

The basal ganglia

Pathways Anatomy

Functions

• Motor • Cognitive • Emotional

• Damage in any area of basal ganglia can produce problems in those three domains.

Cognitive

• Sub cortical dementias • Slowness • Bradyphrenia • Psychomotor retardation • Apathy• Reduced language generation• Secondary frontal effects

Emotional

• Obsessional (sometimes) • Affective instability/frontal• Depression-very common and can be severe• Abulia, akinesis and apathy

Motor

• Abnormality of speed of movement, generally bradykinesia as in Parkinson’s but can be accelerated as in HD or hemibalismus

• Tremor• Chorea • Dystonia • Athetotis • Dystonia• Hemibalismus• Also dysarhtria and clumsiness

Parkinson’s Disease

tremor rest 4-6hz BradykinesiaPoor postural reflexes Festinant gait Response to dopa Presents as assymetric

Chorea

HDSCAsMedications –neuroleptics Rheumatic fever PANDASSt Vitus Dance Congenital benignStorage diseases DRPLAOdd illnessesAutoimmune Phospholipid disease Lupus OCP/pregnancy

Wilson’s DiseaseVery rareMetabolic AR genetics Check condanguinity Liver disorderCopper metabolism goes wrong

Clinically, liver disease, eye disease and dystonic, parkinsonian illness with marked axial and bulbar roblmes

Neuropsychiatric problems,global cognitive decline and personality alterations

Others

Hemibalismus Tics

MCQs

In cerebellar disease • Signs are contralateral • Reflexes are pendular• Hypertonia is the norm • DRPLA is a common cause • There may be malabsorbtion• There are cognitive and affective

changes• Alcohol should be avoided• Rebound is seen • Prosody is affected

In movement disorders• Cognition is always affected.• Depression is common • OCD may be associated with tics • Parkinson’s is normally assymetric in onset• Parkinson’s always responds to dopa • Parkinson plus syndromes have a good

prognosis • Chorea in a forty year old alcoholic with

poor impulse control is worrying• HD shows anticipation • HD is a trinucleotide repeat

The end