| Summary of Cranial Nerve Functions and Tests | ||||
| Nerve | Name | Function | Test | Sign |
| I | Olfactory | Sense of smell | Smelling | Anosmia (loss of sense of smell) |
| II | Optic | Vision | Vision | Loss of vision (partial or total) |
| III | Oculomotor | Motor function of eye and upper eyelid | Eye tracking; pupil response; open and close eye | Decreased tracking; drooping eyelid; decreased pupil constriction |
| IV | Trochlear | Eye motor function | Eye tracking | Diplopia (double vision), especially when looking down |
| V | Trigeminal | Innervates muscles of mastication; general facial sensation | Open and close mouth; assess sensation | Inability to open or close mouth; decreased facial sensation |
| VI | Abducent | Eye motor function | Eye tracking | Medial deviation of affected eye; diplopia (double vision) |
| VII | Facial | Facial muscle motor function; taste; sensation of outer ear | Open and close eyes; forehead wrinkling; taste | Difficulty in opening or closing eyes; decreased taste; difficulty in wrinkling forehead |
| VIII | Vestibulo-cochlear | Hearing and equilibrium | Hearing; balance | Tinnitus; dizziness; loss of balance; decreased hearing |
| IX | Glosso-pharyngeal | Taste | Taste | Decreased taste |
| X | Vagus | Innervates many internal organs | Respiration; speech; swallowing | Dysphonia (difficulty in speaking); dysphagia (difficulty in swallowing) |
| XI | Accessory | Innervates trapezius or sternocleidomastoid | Neck rotation; lateral flexion; shoulder elevation | Loss of function (in neck rotation, lateral flexion, or shoulder elevation) |
| XII | Hypoglossal | Innervates tongue (motor function) | Tongue movement | Decreased tongue motor function; difficulty in speaking |
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