V. Trigeminal nerve

Content last updated 2026-10-07 · 2 min read ·

This is the date the draft was written, not a medical review date.

The trigeminal nerve (CN V) is the main sensory nerve of the face and the motor nerve of the muscles of mastication. It has three sensory divisions: ophthalmic (V1), maxillary (V2) and mandibular (V3), the last also carrying the motor root.

Terminologia Anatomica (Latin): Nervus trigeminus

Function

General somatic afferent (touch, pain, temperature, proprioception) from the face, scalp anterior to the vertex, cornea, nasal and oral mucosa, teeth, and most of the dura. Special visceral efferent to the muscles of mastication, tensor tympani, tensor veli palatini, mylohyoid and anterior belly of digastric.

Nuclei

Three sensory nuclei: the main (principal) sensory nucleus in the pons for touch and discriminative sensation, the spinal trigeminal nucleus extending to the upper cervical cord for pain and temperature, and the mesencephalic nucleus for proprioception from the masticatory muscles. The motor nucleus lies in the pons.

Exit from the skull

V1 leaves through the superior orbital fissure, V2 through the foramen rotundum and V3 through the foramen ovale. The sensory root arises from the trigeminal ganglion in Meckel's cave; the small motor root joins V3 below the ganglion.

Testing

Test light touch and pinprick in all three divisions bilaterally, the corneal reflex (afferent V1, efferent VII), and the jaw jerk. Test the motor part by palpating the masseters and temporalis during clenching and by asking the patient to open the mouth against resistance (the jaw deviates toward the weak side).

Signs of a lesion

Sensory loss in one or more divisions on the face with an absent corneal reflex on the affected side. Motor lesion produces ipsilateral weakness of mastication, with the jaw deviating toward the lesion on opening. A lesion of the spinal trigeminal nucleus or tract gives ipsilateral facial loss of pain and temperature.

Clinical correlations

Trigeminal neuralgia causes brief, severe, electric-shock pain in V2 or V3 territories, often triggered by touch or chewing; compression of the root by a vessel is a frequent cause, and secondary causes such as multiple sclerosis or tumour should be considered. Herpes zoster ophthalmicus involves V1 and threatens the cornea.

Common exam points

V1 superior orbital fissure, V2 foramen rotundum, V3 foramen ovale.
Largest cranial nerve; sensory to face, motor to muscles of mastication (V3 only).
Corneal reflex: afferent V1, efferent VII.
Jaw deviates toward the side of a lower motor neuron lesion of V.
Trigeminal neuralgia: paroxysmal unilateral shock-like pain in V2/V3.

References

Drake RL, Vogl AW, Mitchell AWM. Gray's Anatomy for Students. Elsevier — Tier 3 (textbook)
Moore KL, Dalley AF, Agur AMR. Clinically Oriented Anatomy. Wolters Kluwer, 8th edition (2018) — Tier 3 (textbook)
Haines DE, Mihailoff GA. Fundamental Neuroscience for Basic and Clinical Applications. Elsevier, 5th edition (2018) — Tier 3 (textbook)
Bickley LS. Bates' Guide to Physical Examination and History Taking (Bickley). Wolters Kluwer, 13th edition (2020) — Tier 3 (textbook)

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