Trigeminal Nerve (CN V)

The trigeminal nerve is the largest cranial nerve and the principal sensory nerve of the face. Its name refers to its three divisions: ophthalmic (V1), maxillary (V2), and mandibular (V3). It provides sensation to the face and motor innervation to the muscles of mastication.

Origin

Sensory: trigeminal ganglion; Motor: trigeminal motor nucleus in pons

Foramina

V1: Superior orbital fissure; V2: Foramen rotundum; V3: Foramen ovale

Course

Emerges from lateral pons → trigeminal ganglion in Meckel's cave → three divisions exit through different foramina

Functions

•Facial sensation (touch, pain, temperature)
•Sensation from oral/nasal cavities, teeth, sinuses
•Motor to muscles of mastication
•Afferent limb of corneal reflex and jaw jerk

Branches

V1 Ophthalmic (sensory)

V2 Maxillary (sensory)

V3 Mandibular (mixed - sensory and motor)

Structures Innervated

→V1: Forehead, upper eyelid, cornea, nose dorsum
→V2: Cheek, upper lip, upper teeth, palate
→V3: Lower face, lower teeth, tongue (sensation), muscles of mastication (masseter, temporalis, pterygoids)

Clinical Testing

Test light touch and pinprick in all three divisions. Test corneal reflex (V1 afferent, VII efferent). Test jaw strength and symmetry (motor V3). Assess jaw jerk reflex.

Clinical Relevance

Trigeminal neuralgia causes severe, lancinating facial pain triggered by touch or movement. Herpes zoster can reactivate in the trigeminal ganglion causing shingles. V1 involvement may affect the eye (herpes zoster ophthalmicus).

Study Tips

✓"Standing Room Only" for foramina: V1-Superior orbital fissure, V2-Rotundum, V3-Ovale
✓Only V3 has motor fibers (mandibular = mastication)
✓Trigeminal neuralgia: episodic, electric shock pain, triggered by touch
✓Corneal reflex: V1 afferent, VII efferent - loss indicates V1 or VII lesion

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Trigeminal Nerve (CN V) FAQs

Common questions about this cranial nerve

Most commonly, vascular compression (usually superior cerebellar artery) of the trigeminal root causes demyelination and abnormal signal transmission. This leads to severe, paroxysmal facial pain triggered by innocuous stimuli.

V1 covers forehead to nose bridge; V2 covers cheek, upper lip, upper teeth; V3 covers lower jaw, lower lip, lower teeth, and anterior tongue sensation. Motor testing (jaw strength) only involves V3.

Vesicles on the tip of the nose (Hutchinson's sign) indicate nasociliary nerve involvement. This branch of V1 also supplies the cornea, so its involvement predicts a high risk of ocular complications requiring urgent ophthalmology referral.