The facial nerve: anatomy and common pathology.

The seventh cranial nerve is responsible for much of what makes us individual--the facial expression worn by each individual. The facial nerve (CN VII) is commonly divided into 4 segments for examination: the nucleus and tracts, the cistemal segment that traverses the internal auditory canal, the intratemporal segment (through the bony facial nerve canal), and the peripheral segment. Immediately on leaving the temporal bone at the stylomastoid foramen, the peripheral segment of CN VII becomes much more complicated to follow and is essentially invisible to imaging. Each segment of the facial nerve may be involved by differing pathology. In this report we break down the facial nerve into more easily understood divisions and cover the common pathology of each of these segments.