What is the trigeminal nerve?

Updated: Sep 30, 2019
  • Author: Kim J Burchiel, MD, FACS; Chief Editor: Brian H Kopell, MD  more...
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Answer

Answer

The trigeminal nerve is the largest of all the cranial nerves. It exits laterally at the midpons level and has 2 divisions—a smaller motor root (portion minor) and a larger sensory root (portion major). The motor root supplies the temporalis, pterygoid, tensor tympani, tensor palati, and mylohyoid muscles, as well as the anterior belly of the digastrics muscle. The motor root also contains sensory nerve fibers that particularly mediate pain sensation.

The gasserian ganglion is located in the trigeminal fossa (Meckel cave) of the petrous bone in the middle cranial fossa. It contains the first-order general somatic sensory fibers that carry pain, temperature, and touch. The peripheral processes of neurons in the ganglion form the 3 divisions of the trigeminal nerve: ophthalmic, maxillary, and mandibular (see the image below). The ophthalmic division exits the cranium via the superior orbital fissure; the maxillary and mandibular divisions exit via the foramen rotundum and foramen ovale, respectively. The ophthalmic and maxillary nerves are purely sensory. The mandibular nerve has sensory and motor functions.

Diagram of trigeminal nerve with its 3 main divisi Diagram of trigeminal nerve with its 3 main divisions.

The proprioceptive afferent fibers travel with the efferent and afferent roots. They are peripheral processes of unipolar neurons located centrally in the mesencephalic nucleus of the trigeminal nerve.

For more information about the relevant anatomy, see Trigeminal Nerve Anatomy.


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