Knowledge · Clinical Examination

Cranial Nerve Examination for MRCS Part B: Twelve Nerves in Order

By Dr Richard Miller, MBChB FRCS with the MRCS Part B Questions Team · Reviewed 15 September 2026

In brief

Test the cranial nerves in numerical order: smell, vision and pupils, eye movements, facial sensation and the muscles of mastication, facial movement, hearing, palate and gag, accessory muscles and the tongue.

Examine the cranial nerves in numerical order and say the number of each nerve as you test it. That order is the structure the examiner is marking, and it stops you omitting the olfactory nerve and the gag reflex, which are the two candidates forget under pressure.

Key takeaways

Sit the patient upright at eye level with you, about an arm's length away.
Test the nerves in order I to XII and name each one aloud.
Rinne and Weber use a 512 Hz tuning fork.
The uvula deviates away from the side of a vagus lesion.
In a lower motor neurone hypoglossal lesion the tongue deviates towards the side of the lesion.

How is this station marked in MRCS Part B?

A physical examination station is marked out of 20 across four domains: clinical and technical skill carries 8 marks, and clinical knowledge and its application, communication, and professionalism carry 4 marks each. The examiner also gives the station a separate global rating of pass, borderline or fail.

Two things follow from that split. More than half the marks sit outside your knowledge of the condition, so a silent, technically correct examination scores poorly. And you are signalled at six minutes of the nine to present your findings, so the sequence has to finish inside six.

How do I start the cranial nerve examination?

Gel your hands, introduce yourself, gain consent and position the patient sitting upright with you facing them. Ask the general screening questions before you start testing.

Any change in smell or taste.
Any change in vision or double vision.
Any trouble with hearing or balance.
Any difficulty swallowing or change in the voice.
Look at the face at rest for asymmetry, ptosis, a squint, wasting or abnormal movements.

How do I test the optic nerve?

Cranial nerve II is tested in four parts: acuity, fields, pupils and the fundus.

Acuity: with glasses on, using a Snellen chart at the correct distance, or a hand-held chart at 14 inches, one eye at a time.
Fields: sit opposite the patient, ask them to cover one eye and look at your nose, close your own opposite eye, and bring a target in from the periphery in each quadrant, mapping their field against your own.
Visual inattention: with both eyes open, move one finger or the other and ask which one moved.
Pupils: check size and symmetry, the direct and consensual responses, accommodation, and swing the light between the eyes to look for a relative afferent pupillary defect.
Offer fundoscopy, examining the patient's right eye with your right eye and their left with your left.

How do I test eye movements?

Cranial nerves III, IV and VI are tested together. Steady the patient's chin, ask them to follow your finger with their eyes only, and trace a large H, then bring the finger in towards the nose to test convergence.

Ask at each extreme whether they see double, and look for nystagmus. Remember that the lateral rectus is supplied by VI, the superior oblique by IV and the remainder by III.

How do I test the trigeminal and facial nerves?

Trigeminal sensory: with the eyes closed, touch the forehead, cheek and chin on each side in turn, varying the timing, and ask the patient to say yes when they feel it.
Trigeminal motor: ask the patient to clench the teeth and feel the masseter and temporalis bulk, then ask them to open the jaw against resistance.
Offer the corneal reflex and the jaw jerk rather than performing them.
Facial nerve: raise the eyebrows, screw the eyes shut against resistance, puff out the cheeks, show the teeth and purse the lips.

Forehead sparing separates an upper from a lower motor neurone facial palsy, because the upper face has bilateral cortical representation.

What do Rinne and Weber tests show?

Screen hearing first by whispering a number close to one ear while masking the other, then use a 512 Hz tuning fork. StatPearls notes 512 Hz is chosen because it tests hearing without excessive tactile vibration or rapid decay.

Rinne: place the fork on the mastoid, then 1 to 2 cm from the external auditory canal, and ask which is louder. Air conduction greater than bone conduction is a positive Rinne, found in normal hearing and in sensorineural loss. Bone conduction greater than or equal to air conduction is a negative Rinne and indicates conductive loss.
Weber: place the fork on the vertex or forehead. The sound lateralises to the ear with a conductive loss and away from the ear with a sensorineural loss, and stays central if hearing is normal or symmetrically impaired.
A severe unilateral sensorineural loss can give a false negative Rinne, because the sound crosses to the other cochlea through the skull.

How do I test the lower cranial nerves?

IX and X: ask the patient to open the mouth and say ah, and watch the soft palate rise. Ask about swallowing and listen to the voice, and offer the gag reflex rather than performing it.
XI: ask the patient to shrug the shoulders against resistance for trapezius, and to turn the head to each side against your hand for sternocleidomastoid.
XII: inspect the tongue in the mouth for wasting and fasciculation, then ask the patient to protrude it and to push it into each cheek against your finger.

The uvula deviates away from the side of a vagus lesion, because the intact side of the palate pulls it across. StatPearls states that in an infranuclear hypoglossal lesion the tongue deviates towards the damaged side, because the paralysed muscles cannot resist the intact genioglossus on the other side.

What is the examiner marking, and what goes wrong?

Skipping cranial nerve I because there is no smelling bottle, rather than asking about smell.
Testing the visual fields without closing the corresponding eye, so there is nothing to compare against.
Not asking about double vision during eye movements.
Confusing the Weber result, which lateralises towards a conductive and away from a sensorineural loss.
Saying the tongue deviates away from the lesion, which is the supranuclear pattern, not the lower motor neurone one.
Running out of time because nerves I to III took five of the nine minutes.

MRCS Part B Questions has a cranial nerve examination station with a marked checklist at /Sample-Questions. Reviewed and updated 15 September 2026.

Key evidence

Rinne Test — StatPearls, NCBI Bookshelf (2023)
Neuroanatomy, Cranial Nerve 12 (Hypoglossal) — StatPearls, NCBI Bookshelf (2023)
Candidate Instructions and Guidance Notes: MRCS Part B (OSCE), updated August 2021 — Intercollegiate Committee for Basic Surgical Examinations (2021)

FAQ

Do I have to test all twelve cranial nerves in nine minutes?

Usually the instruction narrows it, for example to the eyes or the lower cranial nerves, so read the stem carefully. If you are asked for all twelve, screen efficiently, offer rather than perform fundoscopy and the gag reflex, and tell the examiner what you are offering so the omission is deliberate rather than accidental.

Which way does the uvula deviate?

Away from the side of the lesion. The intact side of the soft palate still elevates, so it pulls the uvula across towards the normal side. It is the opposite pattern to the tongue in a lower motor neurone hypoglossal lesion, which deviates towards the affected side.

Why is a 512 Hz tuning fork used?

It sits in the middle of the speech frequencies and balances two competing problems. A lower frequency fork produces vibration the patient feels rather than hears, and a higher frequency fork decays too quickly to complete the comparison. 512 Hz gives an audible tone that lasts long enough for the test.

How do I test for a relative afferent pupillary defect?

Swing a bright light rapidly from one eye to the other and back, staying about three seconds on each. In a normal examination both pupils stay constricted. If the affected pupil dilates when the light reaches it, the afferent input on that side is reduced, which indicates optic nerve or extensive retinal pathology.

Should I actually test the gag reflex?

Offer it rather than perform it. It is unpleasant, it can make a patient vomit, and in the station you gain nothing beyond what watching the palate rise on saying ah already told you. Say that you would test it if there were concern about swallowing safety, and move on.

The MRCS Part B Questions Team

Written and maintained by doctors who have sat and scored well at this interview, and reviewed against the current published guideline in each case. Guidance changes — check the source before you rely on a threshold.

Last reviewed 15 September 2026

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