Neurology Revision:Useful background info

Christiane Riedinger May 2014

Table of Contents● Diagnostic reasoning

● Some neuroanatomy

● Examination findings

● Higher functions

Diagnostic Reasoning

Neurological Diagnostic Reasoning● Time course of lesion - TEMPO

● Type of deficit

○ can it be explained by a single lesion?multiple lesions? discrete lesions?

○ recognisable syndrome?

● Locate the lesion - essential: CNS or PNS / UMN or LMN?

● Generate differential diagnosis

● Determine the most likely diagnosis

● Consider the aetiology of disease

● Confirm with investigations

Diagnostic aid: Epidemiology => How likely is the condition?

● Stroke ⅓ ● Migraine ⅓● Carpal tunnel syndrome ¼ ● First fit● TIA● Bell’s Palsy● Essential tremor● Parkinson’s● SAH● Malignant brain tumour● MS● GBS● MND● MG● CJD

Diagnostic Reasoning: Importance of Tempo

● sudden (s-min) - trauma, vascular

● subacute (h-d) - GBS, thrombosis (of a venous sinus), haematoma

● chronic (w-m) - malignancy, degeneration

Definitions of the Locations of Lesions● The UMN is the corticospinal tract/pyramidal system and the cortex up to

the LMN

● The descending corticospinal fibres synapse in the anterior horn cells and become the LMN, they exit via the ventral root and innervate the muscles.

● The extrapyramidal system are the basal ganglia and the striatum* (caudate nucleus and putamen) which are involved in

○ Initiation of movement○ Selection of motor pathways○ Control of postural reflexes

UMN● Increased tone● Increased reflexes● Upwards plantars (Babinski)● Clonus● Spasticity● Forehead spared

● Pyramidal = descending motor neurons (pyramids, i.e. corticospinal tract up to LMN)

● Lesion: immediate flaccid paralysis followed by hyperreflexia and spasticity (clasp-knife?)

● Decreased tone● Decreased reflexes● Downwards plantars (normal)● Fasciculations● Wasting, flaccidity● Complete hemiparesis of face

LMN

Extrapyramidal● Rigidity● If + tremor = cogwheeling● Akinesia● Akathisia

Neurological Pathways: Ascending● Dorsal column - fast conducting fibres (A-beta, heavily myelinated)

○ Touch and proprioception => dorsal root ganglion○ Ascends to brainstem as fasciculus cuneatus (legs, med) and gracilis (arms, lat)○ After nucleus gracilis and cuneatus, decussates as medial lemniscus○ Ascends further to thalamus (laminar nucleus)○ Via internal capsule to somatosensory cortex (postcentral gyrus)○ Brown-Sequard: ipsilateral (to lesion) loss of touch and proprioception

● Spinothalamic tract - slow fibres (A-delta/C fibres, thin)○ Pain and temp => dorsal root ganglion○ Decussates immediately in spinal cord○ Ascends as anterolateral system to thalamus (ventral post. nucleus)○ Via internal capsule to somatosensory cortex (postcentral gyrus)○ Brown-Sequard: contralateral loss of pain and temperature as fibres have not crossed yet

Some Neuroanatomy

Neurological Pathways: Descending

● Corticospinal tract - fastest fibres (A-alpha, heavily myelinated)○ 1* motor cortex (precentral gyrus)○ Descends through internal capsule to form pons○ Gives off branches to V, VII, IX, X and XII○ Enters medulla as pyramids ○ Forms decussation 85% to descend in lateral corticospinal tract○ 15% descend ipsilaterally as ventral corticospinal tract, will cross eventually ○ Synapses in anterior horn cell to become LMN○ Exits via ventral root

● Other descending○ Vestibulospinal tract to neck and trunk for posture and balance○ Reticulospinal tract from reticular formation for posture and coordination○ Rubrospinal tract from red nucleus to inf. olivary nucleus for motor skills learning via

cerebellum

1* Cortices● Only 6% of entire brain surface, most remaining areas association cortices

for higher processing● I Olfactory - Pyriform cortex, uncus (inf. temporal lobe)● II Visual - Striate cortex near calcarine sulcus (17*, occipital lobe)● VIII Auditory - Superior temporal gyrus (41, temporal lobe)● VII, IX Taste - Temporal lobe (38/52?)● Somatosensory - Post-central gyrus● Motor - Pre-central gyrus

Spinal Cord Levels of Limb Movements

Complete Levels LL

HIPFlexion L2,3Extension L4,5

KNEEExtension L3,4Flexion L5,S1

ANKLEExtension (dorsiflexion) L4,5Flexion (plantarflexion) S1,2

Complete Levels ULSHOULDERFlexion C5,6,7Extension C5,6,7Abduction C5Adduction C6,7,8Lat. rotation C5Med. rotation C6,7,8ELBOWFlexion C5,6Extension C7,8ARMSupination C6Extension C7,8WRISTFlexion, Extension C7,8FINGERSLong flexors, extensors C7,8Small muscles of hand T1

For more information, see Consultation Manual “Limb Examination Supplement”

Examination findings

MRC scale of power

0 - no changes

1 - flicker of movement

2 - active movement with eliminated gravity

3 - active movement against gravity (but not resistance)

4 - decreased power against resistance

5 - full power

Nomenclature● hemi half● para lower limbs● tetra/quadra four limbs● paresis weakness● plegia complete paralysis

Features of Increased Tone● Hypertonus/Hypertonicity = abnormally high muscle tone ● Spasticity

○ Velocity and amplitude/force dependent resistance to passive movement caused by hypertonicity, usually with a giveaway in the end

○ Fast flexion and extension of elbow causes sudden increase in tone○ Usually caused by pyramidal (UMN) lesion○ Clasp-knife response (“s.th. snaps shut after initial force”) same as spasticity?

■ Quick decrease of initial hypertonicity upon passive movement ■ Indicates UMN lesion (=Pyramidal tract and cortex)

● Rigidity○ Constant resistance to passive movement○ Usually caused by extra-pyramidal lesion (BG and striatum?)○ If superimposed tremor - cogwheeling, i.e. incremental movement throughout with

increased resistance

Different Kinds of Tremor● Kinetic vs. resting, coarse vs. fast, postural (e.g. outstretched arms), intention● Physiological tremors

○ Anxiety, alcohol, drugs, usually postural● Parkinson’s

○ Coarse resting tremor: 4-6/s○ Pill-rolling tremor○ Resting tremor halted by purposive movements of the body part showing the tremor

● Hyperthyroidism○ 10s physiological resting tremor upon outstretching arms, can be amplified with a piece of paper

● Cerebellar disease○ (Kinetic) intention tremor, coarse: ~5/s○ Exacerbation at the end of movement○ Overshooting?

● Orthostatic tremor○ High frequency tremor: 13-18Hz (therefore difficult to see)○ Predominantly in the legs when in a standing position, and an immediate sense of instability.

Defining Features of Pathological Gaits● Be mindful of mixed pathology, e.g. + joint disease in the elderly

● Hemiplegic gait (pyramidal)○ Leg extended and internally rotated (also foot inversion)○ Circumduction of paretic side (can hear the foot slide)○ Adduction of shoulder, flexion of elbow, thumb in fist (cortical fist)

● Spastic diplegic gait (pyramidal)○ Hip and knee flexed, arms low to middle guard○ Feet internally rotated, knees adducted (touching)○ Bilateral swinging gait

● Neuropathic gait (distal extremities)○ Foot drop, can be externally rotated○ Stepping gait*○ If sensory nerve damage: ataxia, stamping gait**

Defining Features of Pathological Gaits: ctnd

● Antalgic gait (avoid pain)○ Abnormally short stance phase compared to swing phase○ Detect: where is swing phase long and stance short? => affected side

● Myopathic gait* (proximal weakness)○ Pelvis unstable○ Hip drops on non-weight bearing side○ Upper body shifted over w-b side○ Waddling, hyperlordotic gait○ Terendelenburg gait/lurch?

● Parkinsonian gait (hypokinetic)○ Difficulty initiating, then shuffling note early: loss of arm swing○ Patient leaned forward, difficulty turning○ Tremor in upper limb○ Fenestrated gait (picking up of speed), festinant gait (quickened)

Defining Features of Pathological Gaits: ctnd

● Choreiform gait (hyperkinetic)○ Face grimace○ Writing movements○ Gait superimposed onto chorea movements○ No instability/fall as balance maintained

● Ataxic gait* (trunk instability)○ Wide stance○ Trunk unsteadiness, tremor, swaying, sideway jerks○ Difficulty to tandem walk or tiptoe○ Staggering gait

● Stiff/spastic scissoring gait (early spinal cord / UMN lesion**)○ easy tripping, leg dragging○ narrow-based○ stiff reflexes, clonus

Defining Features of Pathological Gaits: ctnd

● Gait apraxia○ inability to carry out complex tasks such as walking

● Gait disturbance by loss of balance or dizziness

Key Cerebellar Symptoms● Ataxia

○ limb - cerebellar hemisphere lesion○ truncal - cerebellar vermis lesion○ gait○ DD

■ cerebellar lesion, caused by MS, tumours, vascular insults, Freidrecih’s ataxia, metabolic, parainfectious

■ sensory ataxia by disorders of proprioception caused by polyneuropathy, dorsal column lesions, drugs

● Ocular symptoms○ Nystagmus, broken smooth pursuit, hypometric (slow) saccadic movement and ocular

dysmetria (saccadic overshoot)● Tremor

○ Kinetic (as opposed to resting) with exacerbation at the end of the movement○ Rebound phenomenon: patient puts arms out and examiner pushes down onto wrist,

observe for swaying● Dysarthria (difficulty to articulate/pronounce language)● Past-pointing during finger-nose test

Mnemonic of Cerebellar Disease● DANISH● Dysdiadochokinesis● Ataxia● Nystagmus● Intention Tremor● Scanning / Staccato or slurred speech (dysarthria)● Hypotonia

Nystagmus● Midline, upon horizontal or vertical gaze● Slow phase = pathological, fast phase = corrective● Peripheral vestibular nystagmus● Central nystagmus● Cerebellar nystagmus

Key Brainstem Symptoms● Eye

○ Nystagmus, internuclear opthalmoplegia, disorder of conjugate gaze, disorder of pupil adaptation?

● Vertigo● Facial weakness● Dysarthria● Gait disturbance● Ataxia● Signs of brainstem death

○ …

Key Spinal Cord Symptoms● Blood supply: anterior supply by single spinal artery=> ischaemic damage,

posterior part anastomoses● Usually bilateral symptoms● Root damage = radicular pain, sensory and motor dysfunction● Distinguish spinal cord level from vertebral level => cord ends at L1!● C6/7 disc prolapse leads to C7 root compression● L4/5 disc prolapse leads to L5 root compression

Named Nerve Palsies● Distal ulnar nerve lesion C8/T1 “Claw hand”, “Klumpke’s paralysis”

○ Symptoms and signs■ 4th and 5th digit: hyperextended metacarpophalangeal joints, flexed interphalangeal joints* ■ There may be waising of the interossei■ Weak finger abduction / adduction■ “Froment’s sign” - can’t grip paper between thumb and closed fist, need to flex DIPJ of thumb

(median nerve)■ Sensory loss over palmar ½ of ring and little finger■ Wrist flexion still intact (median nerve and ulnar nerve)

○ Causes■ Lesion in Guyon tunnel (between pisiform and hook of hamate) “cubital tunnel syndrome”.■ Volkmann’s contracture after supracondylar humeral shaft fracture and compartment syndrome

○ Treatment■ Elbow splinting if from cubital tunnel syndrome, splinting of the hand to avoid permanent

clawing, surgical decompression, medial epicondylectomies, subcutaneous nerve rerouting.

● Ulnar paradox = More proximal ulnar nerve lesion○ Flexor digitorum profundus also lost => reduces the appearance of the claw hand as fingers straighter○ Wrist flexion also lost, radial deviation when attempting to flex the wrist○ Weakened thumb adduction

Named Nerve Palsies● Radial nerve lesion, C5/6 “Erb’s palsy”, “Waiter’s tip”

○ Symptoms and signs■ Forearm extended and pronated■ Shoulder adducted, int. rotated, wrist flexed = “wrist drop”■ Also sensation on flexor side of elbow, wrist and forearm is impaired depending on

the level○ Causes

■ = Injury to upper trunk of brachioplexus*■ Use of crutches in axilla, “Saturday night palsy” = hanging arm over chair■ Spiral fracture of humerus■ Prolonged tourniquet time

● Fibular nerve lesion “Foot drop”○ Nerve supply to ant. and lat. compartment of leg lost○ No extension of ankle (dorsiflexion)

● Median nerve lesion “Hand of benedictine”○ Symptoms and signs

■ First three digits don’t make a fist (therefore looks similar to claw)■ Metacarpophalangeal joint is flexed as patient attempts to make a fist

Named Nerve Palsies: Ctnd.

● Distal Median Nerve Lesion C5-C7 “Carpal Tunnel syndrome”○ Symptoms and signs

■ The patient may experience pins and needles in the fingers in the distribution of the median nerve, i.e. principally in the index and middle fingers and sometimes the thumb. The pain may extend to the forearm (unexplained). The patient may be woken in the middle of the night by these symptoms (pathognomonic). He/she may also experience loss of function due to loss of discriminatory sensation. There may be weakness in abduction, adduction and opposition of the thumb, rarely complete paralysis.

■ LOAF muscles innervated by median nerve: lumbricals (first two), opponens pollicis, abductor pollicis, flexor pollicis brevis

■ Wasting of the thenar eminence. ■ “Tinel’s test/sign”: Tapping over the flexor retinaculum or holding the wrist in a flexed position may induce

paresthesiae.■ “Phalen’s test”: holding wrist in flexion for 30s reproduces/exacerbates symptoms

○ Causes■ Pregnancy, rheumatoid arthritis, osteoarthritis, myxoedema, diabetes mellitus or trauma to the wrist.

Cervical rib. Cervical spondylosis => C6 and C7 root compression■ MEDIAN TRAPS: Myxoedema, enforced/prolonged flexion, diabetic neuropathy, idiopathic, acromegaly,

neoplasms, benign tumours (lipoma, ganglia), RA, amyloidosis, pregnancy/premenstrual oedema, sarcoidosis

● Ix: Neurophysiology● Mx: Splinting, steroid injection, decompression surgery: division of flexor retinaculum

Named Nerve Palsies: Ctnd.

● Long thoracic nerve of Bell lesion C5-C7 “Winged scapula”○ Medial border of the scapula protrudes abnormally○ Serratus anterior paralysed○ Iatrogenic from breast surgery or axillary lymph node clearance

● Dupuytren’s contracture○ Signs and symptoms

■ Flexed appearance of 4th digit, then 5th. Can also affect feet.○ Cause

■ Fibrosis and thickening of the palmar fascia (NOT the tendons)■ Autosomal dominant inheritance, EtOH, phenytoin, cirrhosis, DM, age

○ DD■ Skin contracture due to old laceration, scar or burn

○ Mx■ Surgical when hand can no longer be placed flat onto surface: Fasciectomy =

division of the palmar fascia. ■ Less invasive: needle fasciectomy in outpatient setting■ Least invasive: Collagenase injections

Cranial Nerve Motor Palsies● Complete Ptosis = Lesion of oculomotor nerve (III)

○ Complete paralysis of levator palpebrae superioris○ also affects all eye muscles except lat. rectus (VI, abducens) and sup. oblique (IV, trochlear

nerve)○ Therefore eye underneath points out and down○ If parasymp. affected then pupil dilated as no constrictor pupillae

● Horner’s Syndrome = Loss of sympathetic supply of III○ Partial loss of levator palpebrae superioris○ Constriction of pupil (as parasymp. takes over, no dilation of pupil)○ Anhidrosis over affected side of face○ Enopthalmos

● Bell’s palsy* = distal facial nerve palsy (VII)○ Most commonly in facial canal from int. acoustic meatus to stylomastoid foramen○ Facial asymmetry and unilateral weakness, drooping, dribbling (distal to parotid gland)○ Then with increasingly proximal lesion

■ Occipitalis, stylohyoid and post. belly of digastric lost■ Dampening effect of stapedius lost => sounds are louder■ Loss of taste to ant ⅔ of tongue

Oculomotor Palsies● Complete Ptosis = Lesion of oculomotor nerve (III)

○ Complete paralysis of levator palpebrae superioris○ also affects all eye muscles except lat. rectus (VI, abducens) and sup.

oblique (IV, trochlear nerve)○ Therefore eye underneath points out and down○ If parasymp. affected then pupil dilated as no constrictor pupillae

● Trochlear nerve lesion● Abducent nerve lesions● Internuclear Ophthalmoplegia

Pupillary Defects

● Normal pupils: PERRLA, pupils○ Equal○ Round○ Reactive to light○ And accommodation

● Argyll-Robertson Pupils, specific sign of neurosyphilis and also potential sign of diabetic neuropathy○ Small and irregular○ Absent light reflex○ Intact accommodation reflex○ Depigmentation of the iris

Pupillary Defects: ctnd.

● Holmes-Adie Syndrome/Adie’s tonic pupil, damage to postgang. parasymp., probably viral○ In young woman with absent knee/ankle jerks and impaired sweating○ Large, regular, circular pupil○ Sluggish reaction to light but strong persistent reaction to strong and persistent

stimulus = myotonic pupil, reacts to accommodation

● Marcus Gunn Pupil / Relative Afferent Pupillary Defect○ Detected during swinging flashlight test○ Affected pupil appears to dilate when swinging torch towards it as it actually

constricts less○ Caused by optic nerve lesion or severe retinal disease

Pupillary Defects: ctnd.

● Hutchinson’s pupil○ RIP resulting in uncal herniation through tentorium cerebelli => III

nerve compression resulting in initial constriction of the ipsilateral pupil (parasympathetic irritation, fibres on outside of nerve), later dilation (loss of parasympathetic input). Next, the contralateral pupil will be affected, initially with constriction and finally both pupils will be fixed and dilated indicating a poor prognosis.

● Anisocoria○ Uneven pupil size

● Pupils small, irregular in anterior uveitis● Pupils dilated, oval and fixed in acute glaucoma

Lesions of the Optic Tract

Peripheral Neuropathies: Causes● Trauma, mechanical damage, pressure● 1* axonal degeneration => 2* demyelination

○ toxic○ metabolic => diabetes!○ viral○ nutritional => B12!○ systemic○ Charcot-Marie-Tooth

● 1* demyelinating diseases○ GBS - Guillain Barre Syndrome○ CIDP - Chronic Inflammatory Demyelinating Polyneuritis○ Multifocal Motor Neuropathy and Conduction Block○ Leprosy (sensory)○ Diphtheria (toxin damage)○ Leukodystrophies

● Vascular○ Vasculitis○ RA○ sLE

Peripheral Neuropathies: Types/Distribution

● Symmetrical, e.g. diabetic peripheral neuropathy

● Multifocal - Several deficits, but not of named nerves

● Mononeuritis - Inflammation of single named nerves

● Mononeuritis multiplex - Inflammation of multiple named nerves

● Radiculopathy - Abnormality of single nerve root

● Polyradiculopathy - Abnormality of multiple nerve roots

● Plexopathy - Abnormality of nerve plexus

● Myelopathy - Abnormality of spinal cord (CNS)

● Myopathy - Abnormality of muscles

Peripheral Neuropathies: Ctnd.

● Causes DAD, RUM○ Diabetes○ Alcoholic liver disease○ Drug history○ Rheumatoid arthritis○ Uraemia (=> chronic renal failure?)○ Malignancy

● Also?○ Vitamin B deficiency○ Charcot-Marie Tooth

Peripheral Neuropathies: Ctnd.

● See page 160 of 200 clinical cases● Causes of thickened nerves

○ Amyloidosis, Charcot-Marie-Tooth (Peroneal Muscular Atrophy), Leprosy, Refsum’s, Dejerine-Sottas

● Cause of predominantly motor neuropathy○ GBS, CMT○ Porphyria○ Dapsone, lead, organophorphorous toxicity

● Causes of mononeuritis multiplex (WARDS PLC but order changed here)○ Wegener’s, PAN, Churg Strauss○ Amyloidosis○ RA, T2DM, SLE○ Leprosy

● Predominantly sensory neuropathy○ T2DM, Vitamin B deficiency, chronic renal failure, leprosy

● Diabetic neuropathy○ Symmetrical, predominantly sensory polyneuropathy○ Asymmetrical, predominantly motor polyneuropathy (diabetic amyotrophy)○ Mononeuropathy, autonomic neuropathy

Higher Functions

Problems with Language Processing● Aphasia more severe than dysphasia● Manifests with problems in speech, reading and writing. If pure dysarthria

then reading and writing unaffected but if dysphasia then likely to experience alexia or agraphia.

● VIII lesion Deafness● Lesion in Wernicke’s area* Receptive aphasia (fluent but nonsensical)● Lesion in Arcuate Fasciculus Loss of repetition● Lesion in Broca’s area** Expressive aphasia (obey commands)● Lesion in W. and B. areas Global aphasia● UMN and cerebellar lesion Dysarthria● Cranial nerve lesion VII, X, XII Dysarthria● Impairment of the vocal organs Dysphonia● .. Agnosia

Classification of Memory: Summary acc. to Christiane

● Immediate - short term - long term

● Working memory ~ short term○ Central executive (~attention)○ Auditory store○ Visual store○ Integration

● Long term memory○ Implicit vs. explicit○ Implicit = perceptual (priming) vs. procedural (motor)○ Explicit divided by content, time, modality

■ Episodic vs. semantic (factual) content■ Anterograde (new) vs. retrograde (already formed) time■ Verbal vs. non-verbal modality

Classification of Memory: Summary acc. to Christiane

● Localising Memory○ Hippocampus - forming memories Alzheimer’s○ Left temporal lobe - semantic memory, verbal memory Dementia○ Right temporal lobe - non-verbal memory

● Common Diseases that affect Memory But often diffuse lesions○ Alzheimer’s

■ anterograde = new learning■ then episodic retrograde memory■ then semantic (words lose their meaning)

○ Kosakoff’s■ anterograde memory■ remember the past 15 mins and what happened before their illness started

○ Rapid forgetting in Epilepsy■ memory for autobiographical events is lost when epilepsy is active■ distinct events in past 2 years that are lost■ don’t recognise holiday photos