Facial Nerve Palsy

The VIIth cranial (facial) nerve is largely motor in function (some sensory fibres from external acoustic meatus, fibres controlling salivation and taste fibres from the anterior tongue in the chorda tympani branch). It also supplies the stapedius (so a complete nerve lesion will alter auditory acuity on the affected side). From the facial nerve nucleus in the brainstem, fibres loop around the VI nucleus before leaving the pons medial to VIII and passing through the internal acoustic meatus. It passes through the petrous temporal bone in the facial canal, widens to form the geniculate ganglion (taste and salivation) on the medial side of the middle ear, whence it turns sharply (and the chorda tympani leaves), to emerge through the stylomastoid foramen to supply all the muscles of facial expression, including the platysma.