The cranial nerve examination is often considered one of the most difficult, but with a decent amount of practice and some helpful acronyms along the way you’ll be fine. The important thing to remember is that in an OSCE, you’ll rarely be required to complete an entire cranial nerve exam in one station.
Confirm patient details
Explain the examination – “I’m going to be testing the nerves that supply your face“
Position patient on a chair at eye level, approximately 1 arms length away.
Ask if the patient has any pain anywhere before you begin!
General appearance – comfortable at rest?
Obvious facial asymmetries?
Position of eyes – normal alignment / strabismus
Ptosis – is this unilateral or bilateral?
Abnormality of speech or voice? – dysarthria
Signs around the bed – e.g. hearing aid / glasses
I – Olfactory nerve
Any change in sense of smell? – “What was the last thing you remember smelling?“
With eyes closed, ask patient to identify various scents – e.g. coffee / vinegar
II – Optic nerve
Size – normal size is approximately 2-4mm in diameter (bright light)
Position – assess pupil alignment – misalignment noted in strabismus
1. Stand the patient at 6 metres from the Snellen chart.
2. If patient normally uses distance glasses, ensure they wear them for the assessment.
3. Ask the patient to cover one eye & read to the lowest line they can manage.
4. Visual acuity is recorded as chart distance (numerator) over number of lowest line read (denominator).
5. Record the lowest line the patient was able to read (e.g. 6/6 which is equivalent to 20/20).
6. You can have the patient read through a pinhole to see if this improves vision.
7. Repeat above steps with the other eye.
If patient is unable to read top line at 6 metres (even with pinhole):
1. Reduce the distance to 3 metres from the Snellen chart.
2. Reduce the distance to 1 metre from the Snellen chart.
3. Assess if they can count the number of fingers you’re holding up.
4. Assess if they can see gross hand movement.
5. Assess if they can detect light from a pen torch shone into each each.
If the patient is unable to perceive light, this suggests they are blind.
Direct reflex– shine torch into eye – look for pupillary constriction in that eye
Consensual reflex – shine torch into eye – look for pupillary constriction in opposite eye
Swinging light test– move light in from side of each eye rapidly – relative afferent pupillary defect (RAPD)
1. Ask patient to focus on a distant point (clock on a wall / light switch).
2. Place your finger/object approximately 15cm in front of the eyes.
3. Ask the patient to switch from looking at the distant object to the nearby finger / object.
4. Observe the pupils, you should see constriction & convergence bilaterally.
Say you would use Ishihara charts (often don’t have to actually carry this out in an OSCE setting)
Visual fieldsSit directly facing the patient, approximately 1 metre away.
Visual inattention (visual neglect)
1. Ask patient to focus on your face & not move their head or eyes during the assessment.
2. Hold both arms out, with one hand in the upper right and the other in the upper left quadrant of your visual field.
3. Remind the patient to keep their head still & their eyes fixed on your face.
4. Move one of your fingers (on only one hand) and ask the patient to point at the hand on which the finger is moving.
5. Move the finger on the left and right hand individually in whichever order you prefer.
6. Then move the finger of both hands simultaneously.
7. If patient only reports a finger on one of the hands moving (whilst both are moving simultaneously), it suggests the presence of visual neglect.
8. Repeat the process with your hands in the lower quadrants of vision... Visual fields
1. Ask the patient to cover their left eye with their left hand.
2. You should cover your left eye and be staring directly at the patient (mirror the patient).
3. Ask patient to focus on your face & not move their head or eyes during the assessment.
4. Ask the patient to tell you when they can see your fingertip wiggling.
5. Outstretch your arms, ensuring they are situated at equal distance between yourself & the patient.
6. Position your fingertip at the outer border of one of the quadrants of your visual field.
7. Slowly bring your fingertip inwards, towards the centre of your visual field until the patient sees it.
8. Repeat this process for each quadrant – at 10 o’clock /2 o’clock / 4 o’clock / 8 o’clock.
9. If you are able to see your fingertip but the patient cannot, this would suggest a reduced visual field.
10. Map out any visual field defects you detect.
11. Repeat the same assessment process on the other eye.
1. Darken the room.
2. The patient should have their pupils dilated with short-acting mydriatic eye drops.
3. Ask the patient to fixate on a distant object.
Assess for red reflex
1. Position yourself at a distance of around 30cm from the patient’s eyes.
2. Looking through the ophthalmoscope observe for a reddish / orange reflection in the pupil.
An absent red reflex may indicate the presence of cataract, or in rare circumstances neuroblastoma
Move in closer & examine the eye with the fundoscope
Begin medially & assess the optic disc – colour / contour / cupping
Assess the retinal vessels – cotton wool spots / AV nipping / neovascularization
Finally assess the macula – ask to look directly into the light – drusen noted in macular degeneration
III, IV, VI – Oculomotor, Trochlear & Abducens nerves
Note any evidence of ptosis – oculomotor nerve pathology
1. Ask the patient to keep their head still & follow your finger with their eyes.
2. Move your finger through the various axis of eye movement (“H” shape).
3. Ask the patient to report any double vision.
4. Observe for restriction of eye movement & note any nystagmus.
1. Ask patient to focus on a target (e.g. your pen top).
2. Cover one of the patient’s eyes.
3. Observe the uncovered eye for movement:
- No movement = normal response
- Eye moves temporally = convergent squint
- Eye moves nasally = divergent squint
4. Repeat the cover test on the other eye
V – Trigeminal nerve
Assess light touch and pinprick sensation:
- Forehead – ophthalmic branch (V1)
- Cheek – maxillary branch (V2)
- Jaw – mandibular branch (V3)
Compare left to right for each branch.
Demonstrate sensation on patient’s sternum first, to ensure they understand what it should feel like.
1. Ask patient to clench their teeth & whilst you feel the bulk of masseter & temporalis bilaterally.
2. Ask patient to open their mouth whilst you apply resistance under the jaw – note any deviation (jaw will deviate to side of lesion).
- Ask patient to open mouth loosely
- Place your finger horizontally across the chin
- Tap your finger with a tendon hammer
- Normal = slight closure of the jaw
- Abnormal = brisk, complete closure of the jaw – UMN lesion
Corneal reflex – touch cornea using a wisp of cotton wool – observe for direct/consensual blinking
VII – Facial nerve
Inspect the patient’s face at rest for asymmetry:
Angles of the mouth
Ask the patient to perform the following facial movements…
Raised eyebrows – “raise your eyebrows as if you’re surprised” – observe for asymmetry
Close eyes – “scrunch up your eyes & don’t let me open them” – assess power
Blown out cheeks – “blow out your cheeks & don’t let me deflate them” – assess power
Baring teeth – “can you do a big smile for me?” – note any asymmetry
Purse lips – “can you attempt to whistle for me?” – note any asymmetry
Other things to check…
Inspect external auditory meatus – herpes zoster lesions – Bell’s Palsy
Any hearing changes? – facial nerve supplies stapedius – paralysis results in hyperacusis
Any taste changes? – supplies taste sensation to the anterior 2/3 of the tongue
VIII – Vestibulocochlear nerve
Gross hearing testing
Ask the patient if they have noticed any change in their hearing recently.
Assess each ear individually, standing behind the patient.
1. Explain to the patient that you’re going to say a word or number and you’d like them to repeat it back to you.
2. With your mouth approximately 15cm from the ear, whisper a number or word.
3. Mask the ear not being tested by rubbing the tragus.
4. Ask the patient to repeat the number or word back to you.
5. If the patient repeats the correct word or number, repeat the test at an arms length from the ear (normal hearing allows whispers to be perceived at 60cm).
6. Assess the other ear in the same way.
1. Tap a 512HZ tuning fork & place in the midline of the forehead.
2. Ask the patient where they can hear the sound:
- Normal = sound is heard equally in both ears
- Neural deafness = sound is heard louder on the side of the intact ear
- Conductive deafness = sound is heard louder on the side of the affected ear
1. Tap a 512HZ tuning fork & place at the external auditory meatus & ask the patient if they are able to hear it (air conduction)
2. Now move the tuning fork (whilst still vibrating), placing its base onto the mastoid process (bone conduction)
3. Ask the patient if the sound is louder in front of the ear (EAM) or behind it (mastoid process)
- Normal = Air conduction > Bone conduction (Rinne’s positive)
- Neural deafness = Air conduction > Bone conduction (both air & bone conduction reduced equally)
- Conductive deafness = Bone conduction > Air conduction (Rinne’s negative)
Vestibular testing – “turning test”
Ask patient to march on the spot with arms outstretched & eyes closed:
- Normal – patient remains in the same position
- Vestibular lesion – patient will turn toward the side of the lesion
IX & X – Glossopharyngeal & Vagus nerves
Assess soft palate & uvula:
- Symmetry – note any obvious deviation of the uvula
- Ask patient to say “ahhhh” – observe uvula moving upwards – any deviation?
Gag reflex – you won’t do this in the OSCE, but just make sure you mention it!
Ask patient to cough– damage to nerves IX & X can result in a “bovine” cough
Swallow – ask patient to take a sip of water – note any coughing / delayed swallow
XI – Accessory nerve
Ask patient to shrug shoulders & resist you pushing down – trapezius
Ask patient to turn head to one side & resist you pushing it to the other – sternocleidomastoid
Note any unilateral / bilateral weakness present.
XII – Hypoglossal nerve
1. Inspect tongue for wasting & fasciculation at rest
2. Ask patient to protrude tongue – any deviation?
3. Place your finger on the patient’s cheek & ask to push their tongue against it – assess power
To complete the examination
Say you would…
Perform further testing of any nerves that had abnormal results.
Carry out a full neurological examination of the upper/lower limbs .