The cranial nerve examination is often considered one of the most difficult OSCE stations, but with plenty of practice you’ll be fine. The important thing to remember is that in an OSCE you’ll not be required to complete an entire cranial nerve exam in one station. This guide provides a step by step approach to cranial nerve examination, with an included video demonstration. Check out the cranial nerve examination mark scheme here.
Confirm patient details – name / DOB
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 currently has any pain.
- Pen torch
- Snellen chart
- Ishihara plates
- Cotton wool
- Tuning fork (512hz)
- Glass of water
- Mydriatic eye drops (if necessary)
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 – normally 2 to 4 mm in diameter in bright light and 4 to 8 mm in the dark
Shape – pupils should be round – abnormal shapes can be congenital or due to pathology
Symmetry – note any asymmetry between the pupils (anisocoria)
1. Stand the patient at 6 metres from the Snellen chart.
2. If the patient normally uses distance glasses, ensure these are worn for the assessment.
3. Ask the patient to cover one eye and read to the lowest line they are able to.
4. Visual acuity is recorded as chart distance (numerator) over the number of the 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. If the patient reads the 6/6 line, but gets 2 letters incorrect, you would record as 6/6 (-2).
7. If the patient gets more than 2 letters wrong, then the previous line should be recorded as their acuity.
8. You can have the patient read through a pinhole to see if this improves vision (if vision is improved with pinhole, it suggests there is a refractive element to their poor vision).
9. Repeat above steps with the other eye.
If the patient is unable to read top line at 6 metres (even with pinhole) move through the following steps as necessary:
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.
To best see pupillary reflexes the room should be dimly lit.
Direct pupillary reflex
Shine light into the pupil and observe constriction of that pupil.
Sluggish reaction or lack of constriction may suggest pathology – optic nerve / brain stem / drugs
Consensual pupillary reflex
Again shine a light into the pupil, but this time observe the contralateral pupil.
A normal consensual response involves the contralateral pupil constricting.
Lack of a normal consensual response may suggest:
- Damage to one or both optic nerves
- Damage to the Edinger-Westphal nucleus
Swinging light test
1. Move the pen torch rapidly between the 2 pupils.
This test may detect a relative afferent pupillary defect (RAPD) – caused by damage of the tract between the optic nerve and optic chiasm (e.g. optic neuritis in multiple sclerosis). It’s also known as a “Marcus-Gunn” pupil.
A RAPD can be detected by paradoxical dilatation of the affected pupil when light is shining into it (it should normally constrict).
1. Ask the patient to focus on a distant object (clock on the 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 and convergence bilaterally.
Assess colour vision using Ishihara charts (unlikely to do this in an OSCE setting)
Visual inattention (visual neglect)Sit directly facing the patient, approximately 1 metre away.
1. Ask the patient to focus on your face and not move their head or eyes during the assessment.
2. Hold both arms out, with your fingers in the periphery of both yours and the patient’s field of vision.
3. Remind the patient to keep their head still and 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...
Visual fieldsSit directly facing the patient, approximately 1 metre away.
1. Ask the patient to cover their left eye with their left hand.
2. You should cover your right eye and be staring directly at the patient (mirroring the patient).
3. Ask the patient to focus on your face and 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 and 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 visual field defect.
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 and examine the eye with the fundoscope
1. Begin medially and assess the optic disc – colour / contour / cupping
2. Assess the retinal vessels – cotton wool spots / AV nipping / neovascularization
3. Finally assess the macula – ask the patient to look directly into the light – drusen noted in macular degeneration
III, IV, VI – Oculomotor, Trochlear and Abducens nerves
Note any evidence of ptosis – e.g. oculomotor nerve pathology
1. Ask the patient to keep their head still and follow your finger with their eyes.
2. Move your finger through the various axes of eye movement (“H” shape).
3. Ask the patient to report any double vision.
4. Observe for restriction of eye movement and 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 = divergent squint (exotropia)
- Eye moves nasally = convergent squint (esotropia)
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 and 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
- Explain procedure and gain consent
- Depress lower eyelid
- Ask patient to look upwards
- Touch edge of cornea using a wisp of cotton wool
- Normal response = Direct and consensual blinking
- Not usually required in an OSCE setting
VII – Facial nerve
Inspect the patient’s face at rest for asymmetry:
- Forehead wrinkles
- Nasolabial folds
- Angles of the mouth
Ask the patient to perform specific facial movements
Raised eyebrows – “raise your eyebrows as if you’re surprised” – note asymmetry
Closed eyes – “scrunch up your eyes and don’t let me open them” – assess power
Blown out cheeks – “blow out your cheeks and don’t let me deflate them” – assess power
Smiling – “can you do a big smile for me?” – note asymmetry
Pursed lips – “can you attempt to whistle for me?” – note asymmetry
Other things to check…
Inspect external auditory meatus (EAM) – herpes zoster lesions – Ramsay Hunt syndrome
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 a 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 512 Hz tuning fork and place at the external auditory meatus and 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 and bone conduction reduced equally)
- Conductive deafness = Bone conduction > Air conduction (Rinne’s negative)
1. Tap a 512 Hz tuning fork and 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
Vestibular testing – “turning test”
Ask patient to march on the spot with arms outstretched and eyes closed:
- Normal – patient remains in the same position
- Vestibular lesion – patient will turn towards the side of the lesion
IX & X – Glossopharyngeal and Vagus nerves
Assess soft palate and 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 and 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 and resist you pushing down – trapezius
Ask patient to turn head to one side and resist you pushing it to the other – sternocleidomastoid
Note any weakness
XII – Hypoglossal nerve
1. Inspect tongue for wasting and fasciculation at rest
2. Ask patient to protrude tongue – any deviation?
3. Place your finger on the patient’s cheek and ask to push their tongue against it – assess power
To complete the examination