Trigeminal nerve (CN V)
The trigeminal nerve is the fifth cranial nerve and is while it does provide motor control to the muscles of mastication, its primary role is that of relaying sensory information from the face and head. It is both large and complicated and has multiple brainstem nuclei (sensory and motor) as well as many interconnections with other cranial nerves. It swaps parasympathetic fibers and taste fibers willy-nilly, and divides into dozens of terminal branches.
Nuclei
There are three sensory and one motor nuclei.
The sensory nuclei are arranged in a column which spans from the midbrain through the pons and medulla and into the upper cervical cord.
- mesencephalic nucleus - proprioreceptive fibers for muscles of the face, orbit, mastication, tongue
- main sensory nucleus - located in the upper pons, lateral to the motor nucleus is responsible for touch sensation for all three trigeminal divisions
- spinal nucleus - lower pons to upper cervical cord is responsible for pain and temperature; additionally it receives afferent fibers from the glossopharyngeal nerve and vagus nerve.
The motor nucleus is located in the upper pons and innervates the muscles of mastication as well as mylohyoid and tensor palati.
Intracranial component
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Ophthalmic division (Va)
While passing through the superior orbital fissure the ophthalmic nerve divides into the frontal, lacrimal, and nasociliary nerves. The frontal nerve divides into the supraorbital and supratrochlear nerves. Nasociliary nerve branches include a communicating branch to the ciliary ganglion, short and long ciliary nerves, the posterior and anterior ethmoidal nerves (the latter divides into internal and external nasal branches), and the infratrochlear nerve.
