Neurology Flashcards
Go through the approach to cerebellar examination
Gait
- stagger to affected side unless bilateral or involving vermis
- brad based gait, if subtle - abnrmal gat manifest with tandem walking
LLs
- tone
- heel-shin (make it harder with an arc back to the top)
- big toe to finger
- foot tapping
- Rombergs negative - as sensory propriotception intact
Face
- eyes for nystagmus: jerky horizontal, increased amplitude to side of lesion
- speech: hippopotamus, british constitution, mary had a little lamb (jerky, explosive, irregular syllable separation)
ULs
- extend arms for drift or tremor
- tone looking for hypotonia in acute, unilateral cerebellar disease
- finger-nose looking for intention tremor or past pointing
- look for dysdiadochokinesis
- rebound: lift up arms quickly then stop (they won’t be able to due to hypotonia)
Trunk
- truncal ataxia: fold arms, sitting up, then swing legs over side of ped
- pendular knee jerks
Eyes for papilloedema
- *If obviously unilateral**
- auscultate over cerebellum
- look for cerebellopontine angle tumour (5, 7, 8)
- look for lateral medullary syndrome
- *If midline alone**
- truncal ataxia, abnormal heel-toe, abnormal speech
- think paraneoplastic or midline tumour
- *If bilateral**
- look for MS, Friedreich’s (pes cavus best clue), hypothyroidism (rare)
- ETOH cerebellar degeneration classically spares the arms
Go through the approach to Parkinson’s examination
Movement disorder characetrized by bradykinesia and at least one of rest tremor, rigidity and postural instability
General inspection
- mask-like facies, paucity of movement
- tremor: pill rolling, may be unilateral, is asymmetric when bilateral
- dystonia from medications
- speech: monotonous, soft, poorly articulated
- look for DBS surgery scar/unit
Gait
- Starting, shuffling, freezing, festination.
- Narrow based!
- Reduced arm swing
- ‘pull test’ - unable to maintain balance, loss of postural reflexes
ULs
- tone: cogwheeling or lead pipe. Reinforce by asking for head side to side
- finger-nose and alternating movements
Face
- tremor
- absence of blinking, dribbling saliva, lack of expression
- glabellar tap (finger must be out of line of vision)
- supranuclear gaze palsies
- sweaty brow (autonomic dysfunction)
Other
- write looking for micrographia
- frontal lobe reflexes: grasp, pout, palmar-mental
- higher centres, mini mental state exam
- must at least ask for postural BP
- presence of cerebellar and pyramidal signs suggest MSA
- gaze palsies seen in progressive supranuclear palsy
Presentation
- signs present, degree of disability, whether it’s rigidity or tremor that’s the issue
- state if evidence of postural hypotension, gaze palsy, cognitive dysfunction
Go through the cranial nerve exam
- *First (olfactory)**
- usually not required.
- *Second (A,B, C,D,E F) - optic**
- visual acuity with glasses on
- visual fields: red pin, at arm’s length
- blind spot: disappearance lateral to the centre of field of vision
- colour perception: red desaturation suggests previous optic neuritis
- fundoscopy
- *Third, fourth, and sixth - (oculomotor, torchlear + abducens)**
- *- pupils:** shape, relative sizes, associated ptosis, reflexes (direct and consensual)
- *- RAPD:** look at an object in the distance
- accomodation: distance then hatpin ~15cm from the nose
- *- eye movements**: voluntarily quickly first, then hatpin. Failure, nystagmus, diplopia (and if it improves with covering an eye)
- if variable then test for fatiguability
- saccades: finger and pen 6cm apart: finger -> blink twice -> finger -> quickly at pen. Horizontal and vertical directions
- delay in one or both eyes
- undershoot or overshoot = cerebellar (synonymous to past pointing)
- *Nystagmus**
- cerebellar: unilateral or bilateral. Slow phase to the centre, fast phase in direction of gaze
- associated with dysarthria, limb ataxia, and altered saccades
- peripheral vestibular: unidirectional and frequently horizontal. Worse toward fast phase, better toward slow phase
- associated with abnormal head-impulse test
- monocular: in the setting of weakness of the opposite eye
- vertical: virtually never peripheral
- congenital: dramatic, but patient doesn’t experience world jumping sensation
- multidirectional: most commonly drug toxicity, also generalised cerebellar dysfunction
- *Fifth (trigeminal)**
- ask to test corneal reflex. In from the side, only once each side, looking for a blink, and asking if they can feel it
- in ipsilateral seventh palsy only contralateral will blink (sensation via V), and ipsilateral eye may roll superiorly (bell’s phenomenon)
- *- facial sensation:** ophthalmic, maxillary, mandibular. Pin and light touch
- loss of pain/temp with preserved light touch = medullary or upper cervical lesion
- loss of light touch with preserved pain/temp = pontine*
- motor division: clench teeth and feel masseters; open mouth
- jaw jerk: increased in pseudobulbar palsy
- *Seventh (facial)**
- forehead wrinkle*: preserved in UMN lesion
- tightly shut eyes, grin
- look for ear/palatal vesicle in LMN
- *Eighth (vestibulocochlear)**
- whisper a number for repeating from 0.5m away
- rinne and weber with 256Hz. In conductive look for wax
- don’t miss vestibular assessment in unilateral deafness
- *Ninth and Tenth (glossopharyngeal + vagus)**
- inspect palate for uvular displacement, say ahh for asymmetrical movement (uvula to unaffected side)
- touch the back of the pharynx* on each side with a spatula (hyperactive = gags)
- speak for hoarseness, cough for bovine cough (RLN lesion)
- *Eleventh (spinal accesory)**
- Shrug and feel trap mass
- turn head and feel sternomastoid mass
- *Twelfth (hypoglossal)**
- inspect for wasting and fasciculation (tongue not protruded)
- protrude looking for deviation to weaker side
- *Then**
- depends on findings
- if multiple lower cranial nerve findings look for ENT tumour or signs of surgery/radiotherapy
- say you’d auscultate for carotid or cranial bruits, take the BP, and test urine for sugar
Go through the difference between Bulbar vs Pseudobulbar Palsy. What are the signs and causes?
Go through the eye exam
- *Don’t miss a glass eye**
- suspect if visual acuity zero and no pupillary reaction
- *Inspect**
- corneal: band keratopathy (hypercalcaemia), kayser-fleischer rings (wilson’s)
- sclerae: jaundice, blue, pallor, injected, telangiectasia
- ptosis or strabismus. exophthalmos. xanthelasma
- lid lag
- *Fundoscopy**
- cornea -> lens -> retina
- retinal changes: diabetic, hypertensive. optic atrophy, papilloedema, angioid streaks, detachment, central vein/artery thrombosis, retinitis pigmentosa
- *Fatiguability**
- look up at hat pin or close eyes tightly for 30s
Go through the higher centres examination
Progress very much depends on what the stem is and what you find
- e.g. right sided weakness look for dominant parietal lobe signs
Dysphasia
- Fluent vs non fluent - see diff bscape card
Parietal
-
Dominant parietal lobe (AALF)
- Acalculia (test mental arithmetic)
- Agraphia (test for inability to write)
- Left-right disorientation (eg. place your right hand on your left ear)
- Finger agnosia (iniability to name individual fingers)
- Sensory or visual inattention (neglect/extinction usually more profound if non-dominant lesion)
- astereognosis, agraphaesthesia
- constructional apraxia with clockface
- dressing apraxia with turned inside out pyjama top
- *Temporal**
- short term memory (ball, car, man); medial temporal lobe. Categorical prompts if they can’t get it
- long term memory (when WW2 finished)
Frontal
- reflexes: grasp, pout, palmar-mental
- proverb: rolling stone gathers no moss
- anosmia
- gait apraxia (feet stuck to the ground)
- if lesion then fundi for Foster Kennedy (atrophy in one, papilloedema in the other)
- *Other**
- visual field loss
- carotid bruits
- hypertension
- focal neurological signs
Dysphasia - fluent vs non fluent
Go through the lower limb examination
- *General inspection**
- don’t miss upper limb girdle wasting or IDC
- pes cavus
- gait aids
- back for scars
- *Gait**
- normally
- heel-toe (cerebellar)
- toes (S1); heels (L4/5)
- squat-stand (proximal myopathy)
- don’t miss stooped, festinating, shuffling gait of parkinson’s
- *Sensory**
- if a loss then establish a level on the abdomen
- *Ask for (always complete CNs, ULs, LLs)**
- saddle sensation
- anal reflex
Go through the myotonic dystrophy short case
Autosomal dominant - due to CTG repeats
Continued muscle contraction + delayed relaxation
Distal muscle wasting + weakness
General inspection
- frontal baldness
- triangular facies, partial ptosis
- weak facial muscles - temporalis, masseter, sternocleidomastoid atrophy
Neck
- sternocleidomastoid wasting
- weak neck flexion with intact extension
ULs
- shake hands (grip myotonia, can’t relax)
- percuss thenar eminence (thumb abducts and is slow to relax)
- wasting/weakness, especially of forearm and small hand muscles
- very mild sensory changes if any (associated peripheral neuropathy)
- dec reflexes
- **foot drops in lower limbs
Chest
- gynaecomastia
- look for a PPM
Mental status
- mild cognitive deficit usual
Ask
- to palpate testes for atrophy
- for urine dipstick
- full cardiovascular exam
Compications
- cardiac - conductin, vavuar, cardiomyopathy
- endcrine - DM, hypogonadism, thyroid nodues
- GIT - dysphagia, refux, maabsrtion
- respiratry - hypoventiatin, pneumonia, t2RF
Go through the speech examination
Take careful note of the stem
- e.g. woman has difficulty understanding speech is obvious
- e.g. assess this man’s speech is less so, you need to figure out where you’re heading
Make sure you at no point gesture to what you want, it should all be based on instructions
General inspection
- hemiparesis (or other clear focal deficit)
- gait aids
- word board
Screening (designed to make sure they can understand and process instructions)
- name, age, handedness, how they arrived
- ask them to cough (hoarse)
Comprehension
-
Questions
- simple yes/nos (are you in hospital? are we in your house? are you wearing a coat?)
- double-barrel yes nos (do you put on shoes before socks? do you shut the door before getting into a car?)
-
Commands
- single step: close your eyes; poke out your tongue
- two step: touch your left hand to your right ear (also gives info about right-left disorientation)
- three step: touch your nose, then your chin, then your forehead
- double barrel: point to the ceiling AFTER you point to the floor
Repetition (say what I say)
- blue sky
- baby hippopotamus, british constitution
- mary had a little lamb
- no ifs ands or buts
- zip -> zipper -> zippering
- mamamama (VII)
- kakakaka (X)
- lalalala (XII)
Naming/nominal
- collar -> sleeve -> cuff
- thumb -> ring finger -> knuckle
- watch -> face -> hand
Describe a picture
- looking for neglect of part of the image, speech fluency, speech errors
If Dysphasia, describe as: fluent vs non-fluent; paraphasic errors or not; repetition intact or not; comprehension intact or not
- receptive: fluent but content poor speech
- paraphrasias: phonemic (sink -> sing); semantic (fork -> knife); neoligisms
- expressive: slow and non-fluent; like a telegram
- Brocas (Frontal) - expressive dysphasia - non fluent, can follow commands
-
Wernikes (Tempro-parietal) - receptive - fluent - but cant follow commands
- both MCA territory
If Dysarthria
- LMN: VII, X, XII exam (look for fasciculations; make them rapidly move tongue from side to side looking for slowing)
- UMN: jaw jerk, exaggerated gag reflex, hemiparesis, visual field defect
- cerebellar: nystagmus, intention tremor, gait disturbance
- hypokinetic in Parkinson’s; hyperkinetic in involuntary movement disorders
Go through the upper limb examination
Shake hands firmly. Can’t let go -> myotonia -> myotonic dystrophy (it’d be mean if not)
Drift
- UMN -> downward drift from weakness
- cerebellar -> upwards from hypotonia
- posterior column -> any direction from loss of proprioception
Motor
- UMN, LMN, NMJ, myopathy
- if LMN: anterior horn cell, root, plexus, peripheral nerve, motor neuropathy
Other (always say you’d complete a full examination of CNs, ULs, LLs)
- thickened nerves at ulnar and median
- scars: anywhere, but don’t forget axilla and neck
How does papilloedema present differently to papillitis?
How ought you proceed after finding horner’s syndrome?
Difference in brow sweating
- absence of sweating only when lesion is proximal to the carotid bifurcation
Exclude lateral medullary syndrome
- PICA or vertebral artery occlusion
- nystagmus to side of lesion
- ipsilateral cerebellar signs
- pain/temp loss: ipsilateral face, contralateral limbs
- ipsilateral 9th and 10th lesion
- ipsilateral horner’s
Hoarseness
- RLN
- cranial nerve
Hands
- clubbing
- abduction (C8, T1)
Respiratory
- if any signs of hoarseness of lower brachial plexus lesion
Neck
- lymphadenopathy
- thyroid cancer
- carotid aneurysm or bruit (e.g. fibromuscular dysplasia -> dissection)
Syringomyelia
- dissociated sensory loss (decussating fibres)
- can cause bilateral horner’s
Median nerve lesion
(C6-T1)
- *(C6-T1)**
- *Muscles supplied:**
- all of the muscles on the front of the forearm except flexor carpi ulnaris and half of flexor digitorum profundus
-
LOAF
- Lateral two lumbricals
- Opponens pollicis
- Abductor pollicis brevis
- Flexor pollicis brvis (this sometimes has ulnar innervation)
Clinical features:
- Loss of abductor pollicis brevis with a lesion at or above the wrist - pen touching test (with the hand flat abduct thumb vertically to touch pen)
- Loss of flexor digitorum sublimis with a lesion in or above the cubital fossa - Ochsner’s clasping test (clasp hands firmly together, index finger doesnt flex)
- Sensory loss over the thumb, index, middle and lateral half of the ring finger (plamar aspect only)
Ulnar nerve lesion
(C8-T1)
(C8-T1)
- Wasting of the intrinsic muscles of the hand (except LOAF muscles)
- Weak finger abduction and adduction (loss of interosseous muscles)
- Ulnar claw-like hand (less deformity if lesion higher up)
- Froment’s sign: ask the patient to grasp a piece of paper between the thumb and lateral aspect of the forefinger with each hand - the affected thumb will flex (loss of thumb adductor)
- Sensory loss over the little and medial half of the ring finger (both palmar and dorsal aspects)
What are the causes and findings in argyll robertson pupil?
small and irregular pupils that have little to no constriction to light but constricts briskly to near targets (light-near dissociation).
“Accomodate but don’t react”
Lesion of the iridodilator fibres in the midbrain
Causes
- syphilis
- diabetes mellitus
- alcoholic midbrain degeneration
- other midbrain lesions
Signs
- small, irregular, unequal pupil
- no reaction to light
- prompt reaction to accomodation
- decreased reflexes if tabes associated
What are the causes of absent light reflex with intact accomodation reflex?
What about absent accomodation reflex with intact light reflex?
Absent light reflex with intact accomodation reflex
- midbrain lesion (argyll robertson)
- ciliary ganglion lesion (adie’s)
- parinaud’s (dorsal midbrain: complex findings)
- bilateral anterior visual pathway lesions (bilat afferent pupil deficits)
Absent accomodation reflex with intact light reflex
- cortical lesion (cortical blindness)
- midbrain lesion (rare)
What are the causes of and appearance of jerky vs pendular nystagmus?
Jerky
Horizontal
-
vestibular: horizontal with slow phase toward lesion, fast phase away from the lesion
- accentuated by gaze toward fast phase
- cerebellar: nystagmus to the side of the lesion. Drift toward midline with fast phase in direction of gaze
- INO: nystagmus in the abducting eye
Vertical
- brainstem: upbeat = floor of fourth ventricle; downbeat = foramen magnum
- toxic: phenytoic, alcohol
Pendular
- decreased macular vision
- congenital
What are the causes of anosmia?
Bilateral
- URTI (most common)
- meningioma of olfactory groove (late)
- ethmoid tumours
- trauma (including cribiform plate fracture)
- meningitis
- hydrocephalus
- congenital: Kallmann’s (hypogonadotrophic hypogonadism + anosmia)
Unilateral
- meningioma of olfactory groove (early)
- trauma
What are the causes of carpal tunnel syndrome?
Causes
- idiopathic
- RA
- endocrine: hypothyroidism, acromegaly
- pregnancy
- trauma, overuse
- rare: mucopolysaccharidosis, neurofibromatosis, other deposition type things
What are the causes of cataract?
- Old age
- Endocrine
- diabetes, steroids
- Familial
- dystrophia myotonica
- refsum
- Ocular
- glaucoma
- Irradiation
- Trauma
What are the causes of cerebellar disease: unilateral, bilateral, and midline?
Unilateral
- lesion: tumour, abscess, granuloma
- ischaemia (vertebrobasilar)
- paraneoplastic
- MS
- trauma
Bilateral
- Drugs
- spinocerebellar degenerations: Friedreich’s, SCA, ataxia telangiectasia, FXTAS
- Hypothyroidism
- Paraneoplastic
- MS
- Trauma (punch drunk)
- Arnold-chiari malformation
- ETOH
- large lesion or multiple lesions, multiple infarcts
- rare metabolic diseases
Midline
- paraneoplastic
- midline lesion
Lower limbs only
- rostral vermis by ETOH
What are the causes of chorea?
(Involuntary muscle movements: Also called fidgety movements or dance-like movements usually appear in the hands, feet, and face)
Causes
- Huntington’s (AD)
- Sydenham’s (rheumatic fever)
- Senility
- Wilson’s
- Drugs: OCP, phenytoin, L-dopa, phenothiazines
- Vasculitis/CTD
- Thyrotoxicosis (very rare)
- Hyperviscocity (very rare)
- Viral encephalitis (very rare)
What are the causes of conductive hearing loss (deafness)?
Wax
Otitis media
Otosclerosis
Paget’s disease of bone
What are the causes of extensor plantar response (positive babinski) with absent ankle jerk?
Causes
- subacute combined degeneration
- conus medullaris lesion (compressing cord and hitting S1 nerve root)
- UMN lesion combined with cauda equina or peripheral neuropathy
- syphilis (tabes dorsalis)
- Friedreich’s ataxia
- diabetes (uncommon)
- adrenoleukodystrophy or metachromatic leukodystrophy
What are the causes of fasciculations?
Usually not MND
Causes
- benign idiopathic (by far most common)
- MND
- motor root compression
- tumour neuropathy
- SMA (spinal muscular atrophy), bulbospinal muscular atrophy (Kennedy syndrome)
- any motor neuropathy (less common)
What are the causes of foot drop?
- Common peroneal nerve palsy (can invert foot)
- Sciatic nerve palsy
- Lumbosacral plexus lesion
- L4, L5 root lesion
- Peripheral motor neuropathy
- Distal myopathy
- MND
- Precentral gyrus lesion
Test ankle jerk carefully
- present, think S1 lesion
- absent, think common peroneal nerve palsy
- increased, think UMN or MND
Cannot invert OR evert
What are the causes of horner’s syndrome? due to disruption of sympathetic chain
(triad of ptosis, miosis and anhidrosis)
Partial ptosis and constricted pupil
- reacts normally to light
Central - first order neuron; hypothalamus –> T1
- tumor, stroke, infection
- demyelination, neck trauma
Peripheral - second order neuron; T1 –> superior cervical ganglion
- pancoast tumour, cervical rib, neck surgery
- central lines, aneurysms
Peripheral - third order neuron; superior cervical ganglion –> effector
- ICA aneurysm
- herpes
Causes
- brainstem: CVA (particularly lateral medullary syndrome), syringobulbia, tumour
- retroorbital
- syringomyelia (rare)
- lung: apical carcinoma
- neck: thyroid malignancy, trauma
- carotid: aneurysm, dissection, pericarotid tumour, cluster headache
What are the causes of isolated pain/temperature sensory loss (spinothalamic)?
Causes
- syringomyelia (cape-like)
- Brown-Sequard (contralateral to the lesion)
- anterior spinal artery thrombosis (dorsal columns supplied separately)
- lateral medullary syndrome (contralateral for body, ipsilateral for facial)
- peripheral neuropathy (diabetes, amyloid, Fabry’s, etc)
What are the causes of isolated vibration/proprioception sensory loss (dorsal columns)?
Causes
- subacute combined degeneration (note, has motor findings and can be associated with a peripheral neuropathy
- Brown-Sequard (ipsilateral to the lesion)
- spinocerebellar degeneration (Friedreich’s)
- Multiple Sclerosis
- tabes dorsalis
- sensory neuropathy or ganglionopathy, like in paraneoplastic
- peripheral neuropathy such as in diabetes or hypothyroidism
What are the causes of mononeuritis multiplex?
Separate involvement of >1 peripheral (or cranial, less commonly) nerve
- e.g. radial + common peroneal
Acute
- diabetes
- connective tissue disorder/vasculitis
Chronic
- multiple compressive neuropathies
- sarcoidosis
- CTD or vasculitis (EGPA)
- acromegaly
- leprosy
- Lyme disease
- tumour
- idiopathic
What are the causes of myopathy?
Muscular dystrophies
- duchenne/becker (x-linked), FSH (AD), LG (AR)
- distal dystrophies: autosomal dominant (rare), myotonic dystrophy
Congenital myopathies (rare)
Acquired (PACEPODS)
- Polymyositis (polymyo, dermatomyo)
- Alcohol
- Carcinoma
- Endocrine (hypo/hyperthyroid, cushing’s, acromegaly, hypopit)
- Periodic (hyper/normo/hypokalaemic)
- Osteomalacia
- Drugs (steroids, chloroquine, old HIV drugs, immunotherapies)
- Sarcoidosis
Proximal myopathy + peripheral neuropathy
- paraneoplastic
- alcohol
- CTD
Tests
- CK (highest in Duchenne)
- EMG
- ECG (Duchenne/Becker, myotonic dystrophy)
- muscle biopsy
- TTE (Duchenne/Becker, myotonic dystrophy)
What are the causes of myotonia?
Causes
- myotonic dystrophy
- mytonia congenita (tongue and thenar, recessive form most severe)
- paramyotonia congenita (myotonia after cold exposure or exercise)
What are the causes of ninth and tenth cranial nerve palsies?
Central
- vascular (PICA/vertebral like in lateral medullary syndrome)
- tumour
- syringobulbia
- MND (vagus only)
Peripheral (posterior fossa)
- aneurysm
- tumour
- chronic meningitis
- GBS (vagus only)
Go through the shoulder girdle examination
Usually pointing to FSH muscular dystrophy or root lesion
- don’t miss masseter/temporalis wasting in FSHMD
NO senosry changes in muscular dystrophy
- *Other**
- look for facial weakness
- look for foot drop
- look for abdominal muscle weakness
How does papilloedema present differently to papillitis?
What are the features of Brown-Sequard syndrome? Causes?
Occurs with hemisection of the spinal cord
- *Motor
- **LMN signs ipsilateral at the level of the lesion
- UMN signs ipsilateral below the level of the lesion
- *Sensory
- vibration/propriocetionlossipsilateral** to the lesion
- *- pain/temperature** loss contralateral to the lesion, as these tracts decussate (usually a few segments below the level of the lesion)
- light touch often normal
- may be a band of sensory loss on the ipsilateral side at the level of the lesion
- *Causes**
- MS
- angioma, glioma
- trauma
- myelitis
- postradiation myelopathy
What are the features of Syringomyelia?
So called central-cord syndrome (could also be an intramedullary tumour)
Features
- loss of pain/temperature sensation (cape-like)
- amyotrophy of the arms (if it’s big enough to hit the anterior horn)
- UMN signs in the lower limbs (if it’s big enough to hit the corticospinal tracts)
What is the approach to gait examination? What are the different types of gait?
-
Hemiplegic
- look for UL flexed at elbow with thumb tucked under closed fingers
- circumduction of gait of stiff lower extremity
-
Spastic diplegic (scissoring)
- flexion at hips and knees, hips internally rotated, knees adducted, feet extended
- flexion of both upper limbs (if ULs involved)
- circumduction of gait of stiff lower extremities bilaterally
-
Extrapyramidal (Parkinsonian)
- hestitation starting
- shuffling
- freezing
- festination (can’t catch up with centre of gravity, looks like they’re fall walking)
- propulsion (can’t stop when you pull them toward you gentle)
- retropulsion (opposite of propulsion)
- Cerebellar (wide based, staggering to the affected side)
- Apraxic (feet glued to the floor)
- Posterior Column (wide-based clumsy slapping)
- Distal Weakness (high-stepping)
- Proximal Weakness (waddling)
- Choreiform (involuntary movement disorder)
What’s happening in one and a half syndrome?
One and a half
- PPRF = paramedian pontine reticular formation
Signs:
- (the “one”) horizontial gaze palsy when looking to one side
- (the “half”) impaired adduction on looking to the other side
- Other eye has no horizontal movement
- Other features: contralateral exotropia
Causes: unilateral lesion of the paramedian pontine reticular formation and the ipsilateral medial longitudinal fasciculus OR
lesion of the abducens nucleus (VI) + interruption of the ipsilateral medial longitudinal fasciculus
- stroke, MS plaque or tumour in the dorsal pons
