Figure 7-21.General sensory component (occipital branch) of the facial nerve.
A minor component of CN VII.
The general sensory component consists of afferent fibers which convey general sensory information from the skin of the concha of the external ear and from a small area of skin behind the ear. It may also supplement the mandibular division of CN V in providing sensation from the wall of the acoustic meatus and the outer surface of the tympanic membrane.
Figure 7-22. Central course, general sensory component of CN VII.
The cell bodies of these primary sensory neurons reside in the geniculate ganglion. The peripheral processes of these neurons pass from the skin of the external ear and small region of skin behind the ear through the stylomastoid foramen in conjunction with the fibers of the branchial motor component of CN VII.
They then course through the petrous portion of the temporal bone to the geniculate ganglion.
From the geniculate ganglion, the central processes of these general sensory fibers travel through the facial canal of the petrous portion of the temporal bone and exit the internal acoustic meatus.
The central processes of the general sensory neurons enter the brainstem as part of the nervus intermedius portion of CN VII. The fibers then descend in the spinal tract of the trigeminal nerve to synapse in the spinal nucleus CN V.
Ascending secondary neurons originating from the spinal nucleus of CN V project to the contralateral ventral posteromedial (VPM) nucleus of the thalamus via the anterolateral system.
Tertiary neurons from the thalamus project via the posterior limb of the internal capsule to the sensory cortex of the post-central gyrus.