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Cranial Nerve Examination
What general observations should be made
when looking at the eye?
Ptosis (partial (Horner’s), Complete (CN 3 palsy))
myasthenia gravis, myopathy, age related (weak levator
mms/detached from lid).
Exopthalmos (dysthyroid eye disease. Retro-orbital
mass (rare)).
Enopthalmos (Horner’s). Recession of eyeball within
the orbit due to loss of function of the orbitalis muscle.
What tests should be carried out on pupils?
List some abnormal responses and what
might cause them.
Light reaction (direct & consensual) = Aff = CN2. Eff
= PNS of CN3 B.
Accomodation reaction = Aff = Frontal lobes. Eff =
PNS of CN3 B.
Aniscoria = unequal pupils with norm reactions. Norm
varient.
Holmes-Adie pupil (large, no light reflex, slow
accomodation) =
• Degeneration of ciliary ganglion. Unknown
cause.
• Assoc with loss of DTRs
Relative aff pupilary defect RAPD/Marcus Gunn pupil
(pupil large, swing light test shows one constricts &
other dilates) =
• Lesion ant to optic chiasma (Optic neuritis.
Compression of optic N (rare). Retinal
degenerations (rare).
Argyll-Robertson pupil (pupil small, no light reaction,
normal accomidation) =
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What is Horners syndrome?
List central and peripheral causes of
Horners.
Upper midbrain lesion (v. Rare) (syphilis, diabetes
mellitus, MS (rare)).
Sympathetic denervation resulting in = miosis, partial
ptosis, enopthalmos, loss of hemifacial sweating.
Central lesion
• Hypothalamus.
• Medulla.
• Upper cervical SC (exit at T1).
• Common causes = Stroke (lat medullary
syndrome). Demyelination. Traumer or
syringomyelia (rare).
Peripheral lesion
• Symp chain.
• Sup cervical ganglion.
• Along carotid A.
• Common causes = Pancoat’s tumor (apical
bronchial Ca (lesion at T1 NR, not stellate
gang)). Traumer. Carotid dissection (Rare).
Idiopathic.
Diagram only shows the parasympathetic fibres passing
through the ciliary ganglion. In reality both the
sympathetic and parasympathetic fibres are thought to
pass through the ciliary ganglion but only the
parasympathetic fibres synapse]
And what does the sympathetic nerve supply do?
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What can abnormalities in the visual field
indicate?
it supplies the dilator pupillae muscle (makes
the pupil big)
it supplies the fairly puny Muller’s muscle that
helps keep the eyelid raised.
Unilat defects (retinal/optic N lesion) =
• Constricted field = Chronic papilloedema.
Chronic glaucoma.
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What eye movements are CNS?
What does Diplopia /double vision
Indicate?
What are the types of nystagmus?
What should be checked for if a pt has
nystsgmus?
Scotoma hole in visual field (central) = MS.
Toxic optic neuropathy. Iscaemic optic
neuropathy. Retinal haemorrhage or infarct.
Altidunial defect (confined to upper/lower ½ of
visual field & crossing saggital plane) =
vascular cause (retinal infarct or ischaemic
optic neuropathy).
Bilateral defects (post chiasm/bilat prechiasmal lesions
=
• Bitemporal hemianopias = up qaud more than
low = inf chiasmal compression. Low qaud
more than up = sup chiasmal (usually
craniopharygioma).
• Homonymous qaudrantanopias = upper =
temporal lobe lesion. Lower = parietal lobe
lesion.
• Homonymous hemaniopias. = Incongreous =
lesion of optic tract. Congreous = Lesion post
to lat geniculate body. Macula sparing = lesion
of occipital cortex, or partial lesion of optic
tract or radiation.
Saccadic –very fast movements of eye = Frontal lobe.
Pursuit = occipital lobe.
Vestibular-positional = cerbellar vestibular nuclei.
Convergence = mid-brain.
PNS:
• CN6 = lat rectus.
• CN 4 = sup oblique.
• CN3 = all others.
• Max in direction of gaze of affected mm. False
image = outer, arises in affected eye (N, NM
junction, mm).
• No diplopia = supranuclear, internuclear,
nuclear
Physiological = Looking out of window.
PNS = abnormalities of vestibular system. CN8 N or
nucleus lesion.
CNS = Lesion of central vestibular connections or
cerebellum.
Retinal = Inability to fixate.
Pendular =
• Symetrical, moving at same speed in both
directions.
• Inability to fixate (congenital, may occur
young).
Jerk =
• Fast phase in one direction & slow in other.
Check for =
• Direction of fast phase (horizontal, vertical,
rotatory).
• Pos of eye when when most marked.
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What is vertical nystagmus caused by?
What is horizontal nystagmus caused by?
What other types of unusual eye
movements are there?
What should be tested for CN 5?
2nd degree = occurs in primary pos of gaze.
3rd degree = occurs in with fast phase looking
away from direction gaze.
• Affect abd more than add?
• 1 direction only? Or multi-directional gaze
evoked nystagmus.
• Sustained = CNS.
Fatigue, vertigo symps, dec by fixation = PNS.
• Rare.
• Brainstem lesion.
Up beat =
• Upper brainstem (demyelination, stroke,
Wernicke’s encephalopathy).
Down beat =
• Medullary-cervical junction lesion (ArnoldChiari malformation, syringobulbia,
demyelination ).
Ataxic =
• Fast direction in abd, to slow add.
• Assoc with internuclear opthalmoplegia (MS,
cerebrovascular disaese).
Multidireactional gaze evoked =
• Always CNS (cerebellar or vestibular).
Opsoclonus =
• Rapid oscillations of eyes in horizontal,
rotatory or vertical direction.
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= Brainstem lesion (often a paraneoplastic
syndrome).
Occular bobbing =
• Eyes drift up & down in vertical plane.
• Associated with pontine lesions.
Sensation (pain & light touch)=
• No supply to angle of mandible.
• If loss in 1 or more modalities may be lesion in
sensory ganglion – commonly herpes zosta.
• Loss of sensation in muzzle distribution =
lesion of descending spinal sensory nucleus,
with lowest lvl being outermost (syringomyelia,
demyelination).
• Corneal reflex = neither side contracts = V1
lesion. Only one side contracts = CN7 lesion.
Subjective dec in corneal sense = partial V1
lesion.
mms of mastication =
• pt clench teeth, feel for atrophy.
• Movements (deviation on opening) ART.
• Jaw jerk
What should be tested for CN7?
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CN 7:
• Face = mm of facial expression.
• Ear = N to stapedius, cutaneous sensation.
• Tongue = tase ant 2/3.
• Tear = PNS to lacrimal glands.
• LMNL = all mm effected.
• UMNL = forehead relatively preserved.
Look for face symetry (nasolabial folds, forehead wrinkles. Spontaneous movements (smiling,
blinking ect)).
Ask pt to =
• Show teeth. Whistle. Close eyes tightly (watch eye movement, try to open). Look at ceiling.
Compare forehead strength with lower face.
• LMNL = eyes turn upwards when closing Bell’s phenomenon.
Look at ear (vesicles suggest herpes zosta).
Test taste with saline solution & sugar on cotton wool.
Which CN are assessed by examining the
Cn 9 =
mouth?
• Sensory = post 1/3 tongue; pharynx; mid ear.
• Motor = stylopharyngeus.
CN 10 =
• Sensory = tympanic memb; ext auditory canal
& ext ear.
• Motor = mm of palate; pharynx; larynx (via
recurrent laryngeal N).
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Autonomic = Aff from carotid baroreceptors;
parasymp aff & eff from thorax & ab.
CN12 =
• Motor = intrinsic tongue mm.
What should be looked for in the mouth?
Red beefy = Vit B12 def.
Large = Amyloidosis; acromegaly; congenital
hypothyroidism.
Small =
• With fasiculations & dec speed of movement =
B UMNL mixed with LMNL. MND.
• With fasiculations = B LMNL. MND (prog
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What should be looked for in the pharynx?
Larynx?
bulbar palsy type). Basal meningitis.
Syringobulbia.
• With dec speed of movement = B LMNL –
often assoc with labile emotions. & inc jaw
jerk = pseudobulbar palsy.
Tongue deviates to one side =
• Weakness on side it moves towards.
• With unilat LMNL (rare) = Syringomyelia.
Basal meningitis. Early MND. Foramen
magnum tumour.
• Unilat UMNL (has norm bulk) (more common
than LMNL) = assoc with hemiparesis (strokes,
tumours).
Tongue moves in & out on protrusion = Cerebellar
lesion. Essential tremor. Extrapyramidal syndromes.
Uvula position – observe 1st , say ahh =
• Move up centrally = norm.
• Move to one side = LMNL/UMNL of vagus on
other side.
• Does not move = B palatal mm paresis.
• If no movement with gag reflex & dec pharynx
sensation = CN9 palsy (rare).
Swallow glass of water =
• Smooth cordination of action?
• 2 phases (oral & pharyngeal), any aspiration?
Cough =
• Explosive or gradual?
• Gradual = bovine cough = vocal cord palsy
Speech =
• Vol & qaulity (bubbly voice & cough =
combined cord palsy & pharyngeal pooling due
to CN10 lesion)
• Speech fatigue?
Swallow water =
• Delay b/t oral & pharyngeal phase?
• Followed by coughing & spluttering =
aspiration due to poor airway conduction =
CN10 lesion.