Sensory Root of Trigeminal Nerve

Origin

The sensory root of trigeminal nerve originates in the pons. It emerges from the lateral surface of the pons, roughly where the middle cerebellar peduncle enters the brainstem.

The sensory neurons of the trigeminal nerve have cell bodies located in the trigeminal ganglion. The nuclei targeted by these sensory axons are the pontine nucleus of the trigeminal nerve, the mesencephalic nucleus of the trigeminal nerve, and the spinal nucleus of the trigeminal nerve.

Course

The sensory root of trigeminal nerve runs from the pons to the trigeminal ganglion.

It exits the pons laterally in the body of the middle cerebellar peduncle. From here, the trigeminal nerve runs anteriorly and laterally, crossing over the anterior portion of the petrous ridge of the temporal bone. Just after crossing over, and near the foramen lacerum, the trigeminal nerve runs into the trigeminal ganglion. This is located in the trigeminal impression of the temporal bone, also known as trigeminal (or Mekel’s cave).

Branches

The sensory root of trigeminal nerve forms from three branches. The ophthalmic nerve, also referred to as CN V1, conveys sensory innervation from the forehead and face above the eyes. The maxillary nerve, also referred to as CN V2, conveys sensory innervation from the middle of the face. The mandibular nerve, also referred to as CN V3, conveys sensory innervation from the lower face.

Motor fibers of the trigeminal nerve run in a small motor root just ventral to the sensory root and are not part of the sensory root.

Supplied Structures

The sensory root of trigeminal nerve is similar to the dorsal root of a spinal nerve. It is a sensory root conveying sensory innervation from the face and facial cavities via ophthalmic, maxillary, and mandibular nerve sensory fibers.

The ophthalmic nerve travels into the orbit and conveys general sensory information from the skin of the upper face, roughly from the anterior nose and upper half of the eye, superiorly to the top of the head. This nerve also conveys sensation to the cornea, the mucosa of ethmoid air cells, frontal sinus, and sphenoid sinus, and small portions of the dural folds.

The maxillary nerve travels into the pterygopalatine fossa and innervates the skin of the middle face, roughly from the lower half of the eyes down to the upper lip with its territory arcing up as it moves posteriorly. Other tissues supplied by the maxillary nerve are the maxillary teeth and gingiva, the palate, the nasal cavity, the maxillary sinus, the nasopharynx, the lower lateral nose, and portions of the cranial dura mater.

The mandibular nerve travels into the infratemporal fossa and innervates the skin of the lower face, from the lower lips down to the lower margins of the mandible. Its territory arcs posteriorly and upward, just anterior to the ear. Other tissues innervated by sensory fibers of the mandibular nerve include the mucous membrane lining the cheek, mandibular gingiva, mandibular teeth, and anterior two thirds of the tongue.

List of Clinical Correlates

—Corneal reflex

—Trigeminal neuralgia