The largest component of the facial nerve.
Provides voluntary control of the muscles of facial expression (including buccinator, occipitalis and platysma muscles), as well as the posterior belly of the digastric, stylohyoid and stapedius muscles.
Note the branchial motor components of the facial nerve:
- Branchial Motor
- Clinical Correlation
Origin and Central Course
The branchial motor component originates from the motor nucleus of CN VII in the caudal pons.
Fibers leaving the motor nucleus of CN VII initially travel medially and dorsally to loop around the ipsilateral abducens nucleus (CN VI) producing a slight bulge in the floor of the fourth ventricle - the facial colliculus.
Fibers then course so as to exit the ventrolateral aspect of the brainstem at the caudal border of the pons in conjunction with the nervus intermedius components of CN VII.
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).
The fibers of CN VII pass through the facial canal in the petrous portion of the temporal bone. The course of the fibers is along the roof of the vestibule of the inner ear, just posterior to the cochlea.
At the geniculate ganglion the various components of the facial nerve take different pathways.
Fibers of the branchial motor component pass through the geniculate ganglion without synapsing, turn 90 degrees posteriorly and laterally before curving inferiorly just medial to the middle ear to exit the skull through the stylomastoid foramen.
The nerve to the stapedius muscle is given off from the facial nerve in its course through the petrous portion of the temporal bone.