Trigeminal Nuclei: Afferent and Central Connections

The principal sensory nucleus, which is located in the lateral pons, receives tactile and proprioceptive sensation. It gives off fibers that travel in the trigeminal lemniscus and the uncrossed dorsal trigeminothalamic tract, both of which terminate in the VPM nucleus of the thalamus. It is represented bilaterally in the cortex.

The mesencephalic nucleus contains cell bodies that carry proprioceptive input from masticatory and extraocular muscle spindles. It is the only place in the central nervous system (CNS) where cell bodies of primary sensory afferents are found in the CNS and not in sensory ganglia. The trigeminal mesencephalic nucleus extends from the main sensory nucleus to the superior colliculus of the mesencephalon.

The motor fibers originate in the trigeminal motor nucleus. The sensory and motor roots of the trigeminal nerve leave the pons and pass through Meckel’s cave to form the trigeminal ganglion. This ganglion then divides into the three nerve trunks: the ophthalmic, maxillary, and mandibular nerves. The small motor root passes under the ganglion to join the mandibular nerve.

The ophthalmic nerve (V1) collects pain, temperature, touch, and proprioceptive information from the upper third of the face, top of the nose, scalp regions, and adjacent sinuses. It is joined by filaments from the internal carotid sympathetic plexus and communicates with the oculomotor, trochlear, and abducens nerves as it runs forward in the lateral wall of the cavernous sinus. Near its origin, it gives off a small recurrent tentorial (meningeal) branch to the tentorium cerebelli and then divides into the lacrimal, frontal, and nasociliary branches, which enter the orbit through the superior orbital fissure.

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