Transcript Cranial Nerve Exam

Cranial Nerve Exam
1.Step by step examination taking you through
each individual nerve
2.Common OSCE questions for a cranial nerve
station
3.Video by geeky medics showing you how its
done
NB: OSCE scenario for your year. You’d probably only be asked to do CNI-VI
or from CNVII-XII.
Sammy Sharif. 4th year.
WIPEE

Wash hands

Introduce yourself

Gain Permission

Explain the examination

Expose pt – the pt in the osce will be adequately exposed.
Hi, I’m Sammy Sharif, a 4th year medical student. Today I’ve been asked to perform an
examination of your nerves in your head and neck. Is that ok? Ok great, this will just
involve me having a look at your vision and eye movements, testing some of the muscles
on your face and testing your sensation.
General Inspection

Ptosis/exophthalmos
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Facial symmetry
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Wasting of sternocleidomastoid
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Speech
CNI: Olfactory

“Have you noticed any change in your sense of smell”
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If examiner asks how you would test (very unlikely): Say you would cover each
nostril, ask pt close their eyes and smell something strong like coffee or
peppermint.
CNII: Optic
REMEMBER THIS
GUY!!
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Just remember AFRO
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A: Acuity. Ask pt if they wear glasses/contacts – make sure they’re in/on.
Cover one eye. Stand 6m away (or say you would stand 6m away) with
snellen chart and ask pt which line is the lowest they can read. Then cover
other eye and repeat. 6/12 vision = ptcan read at 6m what a healthy eye can
read at 12m.
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F: Fields. (Hard to explain so I’ll show you). Sit opposite patient. Cover your
left eye with your left hand . Ask patient to cover their right eye with their
right hand. Wiggle your fingers in the 2 quadrants related to your right eye
equidistant between you and slowly bring them towards the middle. Ask pt
when they can see them wiggling. They should see them wiggling the same
time you do. Then keep covering your same eye but with your right hand this
time to allow you to wiggle your fingers in the 2 quadrants on your left.
After 4 quadrants, pt covers their other eye and repeat process.


R: Reflexes. 3 to remember:
o
Pupillary reflex: shine light in one eye – observe for direct response (same pupil
constricts). Then take light away and re-shine it in same eye. Observe for
consensual response (other pupil should constrict). (If you want to be a boss, then
perform swinging flash light test to test for reactive afferent pupillary defect)
o
Corneal Reflex: Just say you would do it with a wisp of cotton wool. Don’t do it in
the OSCE.
o
Accommodation reflex: Ask pt to stare at your finger and follow it as you bring it
close towards their nose. Eyes should converge onto it.
o
NB: Pupillary light and accommodation reflex: afferent arm is optic nerve, efferent
arm is the occulomotor, trochlear, abducens. Test them all here because its easier
to keep all reflexes together
O: Ophthalmoscopy: Just state that you would perform
ophthalmoscopy/fundoscopy. They wouldn’t expect you to do it. It’s a whole
separate station.
CNIII, IV, VI: Occulomotor, Trochlear,
Abducens

Ask pt to keep their head straight and look at your finger with their eyes only.
Make a H pattern and watch their eyes follow it. Ask if there any pain or
double vision while doing that.
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Test for nystagmus. Slow movement of your finger to one side then fast
movement back the other way. Can do it vertically too if you wish.
CNV: Trigeminal
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Muscles of mastication. Ask pt to clench their jaw. Feel their masseter and
temporalis muscle bulk. Ask pt to open jaw against your resistance.
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Sensation: show them how it feels on their sternum, Use cotton wool. Test
in the ophthalmic, maxillary and mandibular areas. COMPARE BOTH SIDES.
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Offer the examiner to do pain and temperature sensation + and the jaw jerk
reflex.
CNVII: Facial
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Just remember the branches and test in that order:
•
To Zanzibar By Motor Car
•
Temporal, Zygomatic, Buccal, Mandibular, Cervical.
•
Temporal: Raise your eyebrows
•
Zygomatic: Scrunch up your eyes
•
Buccal: Blow out your cheeks
•
Mandibular: Whistle
•
Cervical: Stick forward your chin as if you were shaving.
CNVIII: Vestibulocochlear
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Obscure one ear canal by rubbing on tragus. Whisper a number into the other ear an
arm’s length away and ask them to repeat it. Then same for other ear.
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Rinne’s and Weber’s (So many variations):
o
Rinne’s always done first. Make a 512Hz tuning fork buzz. Place the bottom onto the mastoid
process (tell pt this is position 1). Then place the two prongs in front of the ear (tell pt this
is position 2). Ask pt which position they heard it loudest
o
Interpretation of Rinne’s:

Normal hearing or Sensorineural hearing loss: Air conduction is better than bone conduction. This is
termed Rinne’s positive.
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Conductive Hearing loss: Bone conduction is better than air conduction. Rinne’s negative
o
Weber’s: Make tuning fork buzz. Place bottom on the top of the head in the middle. Ask pt
which ear they hear it loudest or is it both the same
o
Interpretation of Weber’s
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Normal: sound heard equally in both ears
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Sensorineural hearing loss: sound loudest in normal ear
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Conductive hearing loss: sound loudest in affected ear
Example:

Pt has conductive hearing loss in right ear. What will Rinne’s and Weber’s
show?
Bone conduction will be better than air conduction when performing Rinne’s
on the right ear. Therefore Rinne’s is negative. Sound will lateralize to the
right ear when performing Weber’s.

Pt has sensorineural hearing loss in right ear. What will Rinne’s and
Weber’s show?
Air conduction will be better than bone conduction when performing Rinne’s
on the right ear. Air conduction will also be better than bone conduction on
the left ear. You would think everything is normal (two positive Rinne’s tests).
But when you do Weber’s - sound will lateralize to the left ear.
CNIX + X: glossopharyngeal + vagus
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Ask pt to cough
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Ask pt to sip some water
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Ask pt to say AAH – look for uvula deviation – uvula deviates to unaffected side.
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Offer gag reflex
CNXI: Spinal Accessory
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Shrug shoulders against resistance
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Move head right and then left both against resistance
CNXII: Hypoglossal
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Ask pt to open their mouth and poke their tongue out. Look for any
fasciculations/deviations.
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If deviated to the right, right hypoglossal nerve affected.
Common Q’s
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A VIth nerve palsy prevents the eye from doing what movement?
Abduction
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What are the characteristic symptoms of a headache due to raised ICP?
• At their worst first thing in the morning.
• Worse on Valsalva (coughing, sneezing, pooing).
• Accompanied with other signs: vomiting, drowsiness, vision
changes.

How would you differentiate between an upper motor neuron VII lesion from a
lower motor neuron VII lesion?
UMN lesion: there is forehead sparing i.e pt would still be able to raise
both eyebrows.
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