Trigeminal Nerve (Fifth Cranial Nerve)
The trigeminal nerve (CN V), the largest CN, possesses both sensory and motor divisions. The sensory portion serves the greater part of the scalp and the forehead, face, eyelids, eyes, lacrimal glands, extraocular muscles, ears, dura mater, and tongue. The motor portion innervates the muscles of mastication through branches of the mandibular division.
Figure 3-20 Diagram of the central pathways and peripheral innervation of CN V. The numbers 1–5 indicate the locations of dermatomes on the face and their corresponding representation in the brainstem.
(Illustration by David Fisher; used with permission from Kline LB. Neuro-Ophthalmology Review Manual. 6th ed. Thorofare, NJ: Slack; 2008:174.)
The CN V nuclear complex extends from the midbrain, through the pons and medulla, to the upper cervical segments, often as caudal as the C4 vertebra. It consists of the following 4 nuclei, listed from rostral to caudal:
main sensory nucleus
spinal nucleus and tract
Important interconnections exist between the different subdivisions of the CN V sensory nuclei and the reticular formation (Fig 3-20).
The mesencephalic nucleus mediates proprioception and deep sensation from the masticatory, facial, and extraocular muscles. The nucleus extends inferiorly into the posterior pons as far as the main sensory nucleus.
Excerpted from BCSC 2020-2021 series: Section 2 - Fundamentals and Principles of Ophthalmology. For more information and to purchase the entire series, please visit https://www.aao.org/bcsc.