Cranial nerves leave the brain and brainstem directly. Testing them helps find where a problem in the nervous system is.
Smell and vision (I, II)
I carries smell. II carries vision: test acuity, visual fields and the pupil light reflex.
Eye movements and pupils (III, IV, VI)
III moves most eye muscles, lifts the eyelid and constricts the pupil. IV and VI move the eye down-in and outward.
Face (V, VII)
V gives facial sensation and chewing. VII moves the face; a stroke often spares the forehead, Bell's palsy does not.
Hearing and balance (VIII)
Hearing and balance. Test with finger rub, Weber and Rinne.
Throat, shoulders and tongue (IX to XII)
IX and X raise the palate and control swallowing. XI shrugs the shoulders and turns the head. XII moves the tongue.
| Nerve | Main job | Quick test |
|---|---|---|
| I Olfactory | Smell | Familiar scent (optional) |
| II Optic | Vision | Acuity, fields, pupils |
| III Oculomotor | Eye movement, pupil, eyelid | H pattern, pupils |
| V Trigeminal | Face sensation, chewing | Light touch, clench jaw |
| VII Facial | Face movement | Raise brows, smile |
| VIII Vestibulocochlear | Hearing, balance | Finger rub, Weber, Rinne |
| IX, X | Palate, swallowing | Say "ah" |
| XI Accessory | Shoulder shrug, head turn | Shrug against resistance |
| XII Hypoglossal | Tongue | Stick out the tongue |
At the bedside
Use the same order every time and compare both sides.
Related guides
Written by Making Synapses. Topic reference: OpenStax, Anatomy and Physiology 2e (no text adapted).