Trigeminal nerve (V)

At a glance

English

Trigeminal nerve (V)

Latin (TA2)

Nervus trigeminus (V)

System

Nerve

Region

Head

Side

Paired, left and right

About the trigeminal nerve (v)

Cranial nerve V is the main sensory nerve of the head and also the motor nerve for chewing. Its name means 'three twins', because on each side it divides into three great branches: V1 (ophthalmic), V2 (maxillary) and V3 (mandibular). V1 and V2 are wholly sensory; V3 carries both sensory and motor fibres.

The nerve is attached to the lateral pons by a large sensory root and a small motor root. The sensory root runs forwards to the trigeminal ganglion, which lies in a dural pocket, Meckel's cave, on the petrous apex and holds the cell bodies of the sensory fibres. The three divisions spread from the front of the ganglion and leave the skull by separate openings: V1 through the superior orbital fissure, V2 through the foramen rotundum and V3 through the foramen ovale. The motor root slips beneath the ganglion without relaying and joins V3.

V1 serves the forehead and front of the scalp, the upper lid, cornea and conjunctiva, the bridge and tip of the nose and the frontal sinus. V2 serves the lower lid, cheek, side of the nose, upper lip, upper teeth and gums, palate and the maxillary sinus. V3 serves the lower lip, chin, lower teeth, the lower face apart from the angle of the jaw, part of the outer ear and, through the lingual nerve, ordinary sensation from the front of the tongue; taste there travels in the chorda tympani. Motor fibres of V3 supply masseter, temporalis, the two pterygoids, mylohyoid, the anterior belly of digastric, tensor veli palatini and tensor tympani.

Centrally the sensory fibres end in a long nuclear column: the principal nucleus in the pons for fine touch, the spinal nucleus down to the upper cervical cord for pain and temperature, and the mesencephalic nucleus for proprioception from the jaw, which also drives the jaw jerk. Because the territories of the divisions barely overlap, a local anaesthetic block numbs a sharply bounded area. Trigeminal neuralgia causes brief, severe stabs of facial pain. A peripheral V3 lesion weakens chewing on one side, and the opened jaw swings towards the weak side. In lateral medullary (Wallenberg) syndrome, pain and temperature are lost from the face on one side and the body on the other.

Course and supply

Arises from

Attached to the lateral surface of the pons by a large sensory root and a small motor root; the sensory cell bodies lie in the trigeminal ganglion.

Ends in

Divides at the ganglion into the ophthalmic, maxillary and mandibular nerves, which leave the skull by the superior orbital fissure, foramen rotundum and foramen ovale.

Supplies

Sensory to the face, front of the scalp, eye, nasal and oral cavities, teeth and much of the dura; motor to the muscles of mastication, mylohyoid, anterior digastric, tensor veli palatini and tensor tympani.