Visceral Motor

Overview

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Figure 7-12. Overview of visceral motor components of the facial nerve.

Parasympathetic component of the facial nerve.

Consists of efferent fibers which stimulate secretion from the submandibular, sublingual, and lacrimal glands, as well as the mucous membranes of the nasopharynx and hard and soft palates.

Origin and Central Course

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Figure 7-13. Visceral motor component of the facial nerve: origin and central course.

The visceral motor component originates from a diffuse collection of cell bodies in the caudal pons just below the facial nucleus known as the superior salivatory nucleus.

Fibers course so as to exit the ventrolateral aspect of the brainstem at the caudal border of the pons as part of the nervus intermedius portion of CN VII. these fibers do not loop around the abducens nucleus.

The nervus intermedius exits the brainstem just lateral to the branchial motor component.

Intracranial Course

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Figure 7-14. Intracranial course, visceral motor component of the facial nerve.

Upon emerging from the ventrolateral aspect of the caudal border of the pons, all of the components of CN VII enter the internal auditory meatus along with the fibers of CN VIII (vestibulocochlear nerve).

Within the facial canal the visceral motor fibers divide into two groups to become the greater petrosal nerve and the chorda tympani:

The greater petrosal nerve supplies the lacrimal, nasal, and palatine glands.

The chorda tympani supplies the submandibular and sublingual glands.

Course of the Greater Petrosal Nerve

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Figure 7-15a. Course of the greater petrosal nerve through the temporal bone.

At the geniculate ganglion the greater petrosal nerve turns anteriorly and medially exiting the temporal bone via the petrosal foramen and entering the middle cranial fossa.

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Figure 7-15b. Extra-cranial course of the greater petrosal nerve.

The greater petrosal nerve passes deep to the trigeminal ganglion to enter the foramen lacerum. The nerve traverses the foramen and enters a canal at the base of the medial pterygoid plate in conjunction with sympathetic fibers (deep petrosal nerve) branching from the plexus following the internal carotid artery. The parasympathetic and sympathetic fibers together make up the nerve of the pterygoid canal.

Upon exiting the pterygoid canal, pre-ganglionic parasympathetic fibers of CN VII synapse in the pterygopalatine ganglion which is suspended from the fibers of the maxillary division of the trigeminal nerve (V2) in the pterygopalatine fossa.

Post-ganglionic parasympathetic fibers then follow the fibers of V2 to reach the lacrimal gland (via the lacrimal nerve) and the mucous membranes of the nasal and oral pharynx.

Course of the Chorda Tympani

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Figure 16a. Course of the chorda tympani, inner ear.

The pre-ganglionic fibers of the chorda tympani branch from the other fibers of CN VII as they pass through the facial canal just posterior to the middle ear.

The fibers pass through the middle ear in close relationship with the tympanic membrane and exit the base of the skull to enter the inferotemporal fossa:

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Figure 7-16b. Distal course and final innervation of the chorda tympani.

In the inferotemporal fossa the chorda tympani joins the fibers of the lingual branch of the mandibular division of CN V (V3).

CN VII pre-ganglionic fibers synapse in the submandibular ganglion suspended from the lingual nerve (V3). Post-ganglionic fibers then either enter the submandibular gland directly or again follow the lingual nerve before branching to innervate the sublingual gland: