Cranial nerve examination !

Exam technique

Simple tests that check the twelve nerves that leave the brain and brainstem.

Updated 2026-11-01

See it in 3D: Olfactory nerve (I) · Optic nerve · Oculomotor nerve (III) · Trochlear nerve (IV) · Trigeminal nerve (V) · Abducens nerve (VI) · Facial nerve (VII) · Vestibulocochlear nerve (VIII) · Glossopharyngeal nerve (IX) · Vagus nerve · Accessory nerve (XI) · Hypoglossal nerve (XII)

What it is

The twelve cranial nerves control smell, vision, eye movements, facial sensation and expression, hearing, swallowing and the tongue. Testing them localises lesions in the brainstem, the skull base or along each nerve. The combination of nerves involved and long-tract signs tells the level of the lesion.

Landmark anatomy

Nerves I and II arise from the forebrain; nerves III to XII arise from the brainstem (midbrain, pons and medulla).
The forehead is supplied by both motor cortices, which is why a central facial lesion spares it.
Pupillary light reflex: input through nerve II, parasympathetic output through nerve III.
Gag reflex: input through nerve IX, motor output through nerve X.

Technique, step by step

Sit the patient facing the examiner at the same height, in good light.
I: with the eyes closed and one nostril blocked, bring a familiar smell to the other.
II: acuity with a chart for each eye, visual fields by confrontation in all four quadrants, and fundoscopy.
III, IV and VI: look at the lids and pupils; the patient follows a target in an H pattern without moving the head and is asked about double vision.
V: touch the forehead, cheek and chin on both sides; feel the masseters while the patient clenches the teeth.
VII: ask the patient to wrinkle the forehead, close the eyes tightly against resistance, puff out the cheeks and smile.
VIII: whisper a number into each ear while the other is covered; Rinne and Weber if hearing is reduced.
IX and X: ask the patient to say 'aah' and watch the palate rise symmetrically; assess voice and swallowing.
XI: turn the head and shrug the shoulders against the examiner's hand.
XII: stick out the tongue and move it side to side; look for deviation, wasting and fasciculations.

The twelve cranial nerves at the bedside

Nerve	How to test	Abnormal finding
I olfactory	Smell coffee or soap with each nostril in turn	Anosmia (trauma, COVID-19, Parkinson disease, frontal tumour)
II optic	Visual acuity, confrontation fields, pupils and fundoscopy	Reduced acuity, field defect, afferent pupil defect, papilloedema
III oculomotor	Follow a target in an H pattern; pupils and lids	Ptosis, eye 'down and out', dilated pupil if compressive
IV trochlear	Look down with the eye adducted	Vertical diplopia on going downstairs; head tilt
V trigeminal	Touch and pain in all three divisions, corneal reflex, jaw clench	Facial numbness, absent corneal reflex, jaw deviates to the weak side
VI abducens	Lateral gaze of each eye	Eye fails to abduct; horizontal diplopia
VII facial	Wrinkle the forehead, close the eyes tightly, smile	Peripheral: whole half of the face; central: forehead spared
VIII vestibulocochlear	Whispered voice, Rinne and Weber; nystagmus	Hearing loss, vertigo, nystagmus
IX glossopharyngeal	Gag reflex (sensory limb)	Reduced gag on one side, dysphagia
X vagus	Say 'aah': palate and uvula rise; voice	Uvula deviates to the healthy side, hoarse or nasal voice
XI accessory	Turn the head and shrug the shoulders against resistance	Weak sternocleidomastoid or trapezius
XII hypoglossal	Stick out the tongue; wasting and fasciculations	Tongue deviates towards the side of the lesion

Abnormal findings

Weakness of the whole half of the face with inability to close the eye: peripheral facial palsy, such as Bell palsy.
Ptosis with a dilated pupil and the eye turned down and out: third nerve compression, an emergency.
Ptosis and diplopia that worsen at the end of the day with normal pupils: suggests myasthenia gravis.
Dysarthria, dysphagia and a wasted, fasciculating tongue: bulbar palsy (lower motor neuron).

Common errors

Using irritant smells such as ammonia: they stimulate the trigeminal nerve, not the olfactory nerve.
Confusing ptosis with facial weakness; eye closure depends on nerve VII, lid elevation on nerve III and the sympathetic pathway.
A bilaterally absent gag reflex is common in healthy older people.

Test yourself

Think of the answer, then tap the question to see it.

How is a central facial palsy told apart from a peripheral one?

A central palsy (for example, a stroke) spares the forehead because it is supplied by both hemispheres; a peripheral palsy, such as Bell palsy, weakens the whole half of the face.

Which way does the tongue deviate in a twelfth nerve lesion?

Towards the side of the lesion, because the healthy genioglossus pushes the tongue towards the weak side.

What does a dilated pupil with ptosis and the eye down and out indicate?

A compressive third nerve palsy, for example from a posterior communicating artery aneurysm or uncal herniation; it needs urgent work-up.

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See it in 3D

The structures of Durgical's 3D anatomy where it is found.

← All of the clinical exam

Educational content on the clinical exam; it is learned and practised under supervision. It does not replace assessment by a health professional and is not for self-diagnosis.

Sources: How To Assess the Cranial Nerves (MSD Manual Professional Edition, 2024); 16.3 The Cranial Nerve Exam (OpenStax, Anatomy and Physiology 2e, 2022); 26.2 Physical Assessment - Clinical Nursing Skills (OpenStax, 2024).

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Representative model, for educational purposes only.