Trigeminal-facial nerve communications. Their function in facial muscle innervation and reinnervation.

Abstract

Peripheral trigeminal-facial communicating rami are trigeminal fibers accompanying facial nerve branches. Rami participate in innervation of facial muscles, mediating facial proprioception, and deep sensibility. Sparse extrapetrous facial nerve afferents have smaller diameters than typical muscle spindle nerve fibers; however, rami contain larger fibers. Facial kinesthetic sense probably derives from cutaneous and mucosal receptors having cell bodies in trigeminal and geniculate ganglia, their central processes terminating in the trigeminal sensory nucleus. Denervated facial musculature may be reinnervated other than by regeneration of the affected facial nerve. Transsagittal sprouting of the opposite facial nerve may provide partial reinnervation. Some facial nerve fibers may utilize alternate routes over trigeminal branches; collateral sprouting of these accessory motor fibers may provide some reinnervation. Systematic clinical observations and experiments using modern electrophysiological techniques could answer questions suggested by this review and establish functional significance of trigeminal-facial communications.