Reference — Neurology
Cranial Nerves Reference
All 12 cranial nerves (CN I–XII) — name, type, main function, bedside assessment method, and clinically important abnormal findings for nurses.
Educational use only. This material supports nursing education and exam review. It is not medical advice and is not a substitute for clinical judgment, institutional policy, or medical direction. Always follow facility protocols and current provider orders.
Memory tip: “Oh, Oh, Oh, To Touch And Feel Very Good Velvet, AH!” — Olfactory, Optic, Oculomotor, Trochlear, Trigeminal, Abducens, Facial, Vestibulocochlear, Glossopharyngeal, Vagus, Accessory, Hypoglossal. Type mnmonic: “Some Say Marry Money But My Brother Says Big Brains Matter More” (S = sensory, M = motor, B = both).
Quick Reference Table
| CN | Name | Type | Primary Function |
|---|---|---|---|
| CN I | Olfactory | Sensory | Smell |
| CN II | Optic | Sensory | Vision |
| CN III | Oculomotor | Motor | Eye movement (superior, inferior, medial rectus; inferior oblique); upper eyelid elevation (levator palpebrae); pupil constriction (parasympathetics) |
| CN IV | Trochlear | Motor | Superior oblique muscle — rotates eye inward and downward |
| CN V | Trigeminal | Both | Sensory: face sensation (three divisions — V1 ophthalmic, V2 maxillary, V3 mandibular) |
| CN VI | Abducens | Motor | Lateral rectus muscle — abducts the eye (looks outward laterally) |
| CN VII | Facial | Both | Motor: facial expression muscles |
| CN VIII | Vestibulocochlear (Acoustic) | Sensory | Hearing (cochlear branch); balance and spatial orientation (vestibular branch) |
| CN IX | Glossopharyngeal | Both | Sensory: taste posterior 1/3 tongue; pharyngeal sensation |
| CN X | Vagus | Both | Motor: pharynx, larynx, soft palate |
| CN XI | Accessory (Spinal Accessory) | Motor | Sternocleidomastoid (neck rotation) and trapezius (shoulder shrug) |
| CN XII | Hypoglossal | Motor | Tongue movement |
Cranial Nerve Detail
Function: Smell
Bedside test: Ask patient to identify a familiar odor (coffee, vanilla) with one nostril occluded at a time
Abnormal findings: Anosmia (loss of smell): head trauma (sheering of olfactory fibers through cribriform plate), olfactory groove meningioma, COVID-19
Function: Vision
Bedside test: Visual acuity (Snellen chart or finger counting); visual fields to confrontation (wiggling fingers in each quadrant); pupillary afferent limb (swinging flashlight test for RAPD)
Abnormal findings: Vision loss, visual field defects (hemianopia), optic neuritis (MS), papilledema (elevated ICP visualized on fundoscopy)
Function: Eye movement (superior, inferior, medial rectus; inferior oblique); upper eyelid elevation (levator palpebrae); pupil constriction (parasympathetics)
Bedside test: Follow finger in H-pattern (tests eye movement); pupil reactivity to light; eyelid position (ptosis?)
Abnormal findings: CN III palsy: ptosis, eye deviated down-and-out, fixed and dilated pupil. Uncal herniation compresses CN III → CRITICAL EMERGENCY
Function: Superior oblique muscle — rotates eye inward and downward
Bedside test: Ask patient to look down and inward; patient may report vertical diplopia going down stairs
Abnormal findings: Vertical diplopia (double vision when looking down); head tilt to compensate. CN IV palsy: common after head trauma (longest intracranial course, most vulnerable)
Function: Sensory: face sensation (three divisions — V1 ophthalmic, V2 maxillary, V3 mandibular). Motor: muscles of mastication (jaw movement)
Bedside test: Light touch and pinprick to each facial division bilaterally; corneal reflex (afferent limb of blink reflex); ask patient to clench jaw (palpate masseter)
Abnormal findings: Facial numbness, jaw deviation (ipsilateral), absent corneal reflex, trigeminal neuralgia (lancinating facial pain), brainstem stroke
Function: Lateral rectus muscle — abducts the eye (looks outward laterally)
Bedside test: Test lateral gaze (finger tracking to far left and far right); assess for inability to abduct eye
Abnormal findings: Lateral gaze palsy — eye cannot abduct past midline; diplopia on lateral gaze. CN VI is the earliest cranial nerve affected by elevated ICP (long intracranial course)
Function: Motor: facial expression muscles. Sensory: taste anterior 2/3 tongue. Parasympathetic: lacrimal and salivary glands
Bedside test: Smile, raise eyebrows, close eyes tightly, puff cheeks, show teeth. Assess for asymmetry.
Abnormal findings: Bell palsy (peripheral): entire ipsilateral face weak — cannot wrinkle forehead. Central (stroke): LOWER face weak only (forehead spared — dual cortical innervation protects forehead). Taste impairment anterior tongue.
Function: Hearing (cochlear branch); balance and spatial orientation (vestibular branch)
Bedside test: Whisper test or finger rub at ear level for hearing; Weber and Rinne tests (tuning fork); assess for nystagmus (vestibular dysfunction)
Abnormal findings: Sensorineural hearing loss, tinnitus, vertigo, nystagmus. Acoustic neuroma (vestibular schwannoma) causes progressive unilateral sensorineural hearing loss
Function: Sensory: taste posterior 1/3 tongue; pharyngeal sensation. Motor: stylopharyngeus (pharynx elevation). Parasympathetic: parotid gland. Afferent limb of gag reflex.
Bedside test: Gag reflex (CN IX = afferent limb, CN X = efferent limb); assess swallowing; taste posterior tongue
Abnormal findings: Loss of gag reflex, dysphagia, glossopharyngeal neuralgia (pharyngeal pain triggered by swallowing). Assessed together with CN X
Function: Motor: pharynx, larynx, soft palate. Parasympathetic: heart, lungs, GI tract. Sensory: viscera, posterior pharynx. Efferent limb of gag reflex.
Bedside test: Say 'aah' — uvula should rise midline. Hoarseness check. Gag reflex (efferent limb). Assess for dysphagia.
Abnormal findings: Uvular deviation away from lesion side; hoarseness (vocal cord palsy); dysphagia; absent gag reflex. Bilateral CN X injury: life-threatening
Function: Sternocleidomastoid (neck rotation) and trapezius (shoulder shrug)
Bedside test: Shoulder shrug against resistance (trapezius); turn head against resistance each direction (SCM)
Abnormal findings: Shoulder drop; weakness turning head contralaterally; CN XI palsy from neck surgery, lymph node dissection, or cervical cord injury
Function: Tongue movement
Bedside test: Protrude tongue and move side to side; assess for deviation, atrophy, fasciculations
Abnormal findings: Tongue deviates toward the side of the LESION (ipsilateral) in peripheral palsy (CN XII injury). Note: in stroke (UMN lesion), tongue deviates toward the WEAK SIDE (contralateral to lesion) — same direction as arm/leg weakness
Clinically Critical CN Findings
- ✦CN III (fixed dilated pupil) = uncal herniation until proven otherwise. CRITICAL emergency — notify provider STAT.
- ✦CN VI (lateral gaze palsy) is the earliest CN affected by elevated ICP — a localizing sign for raised ICP.
- ✦CN VII: bell palsy (peripheral) = entire face weak including forehead. Stroke (central) = lower face only, forehead spared.
- ✦CN IX + X tested together: absent gag reflex + uvular deviation + dysphagia = brainstem or glossopharyngeal/vagus palsy.
- ✦CN XII: tongue deviates toward the lesion in peripheral CN XII palsy; toward the weak limb side in central (stroke) lesion.
- ✦Acute onset of CN VII, IX, X, XII palsies together (bulbar palsy) = brainstem event or GBS. Respiratory compromise is imminent.
Related Resources
Standards & sources
Fact-checked Jun 21, 2026This page is written to align with American Heart Association / American Stroke Association (AHA/ASA) · American Association of Neuroscience Nurses (AANN). It is an educational summary, not a citation of any single document — always verify specific doses, values, and protocols against current guidelines and your facility policy. How we source content →