The Human Facial Nerve; Quantitative Features

Abstract

Fresh cadaver specimens of 2 facial nerves were fixed and embedded for plastic section light and electron microscopy. The transverse fascicular area of both nerves had approximately 12 000 myelinated nerve fibers. Their numbers appeared to be about 1 800 higher in the tympanic segment than in the cisternal segment. The diameters of myelinated nerve fibers showed a bimodal distribution. The peak of small fibers was 4 microns, of large fibers 8 microns. Most small diameter fibers were concentrated in the peripheral zones. The percentage of unmyelinated axons in the zones formed mainly by small diameter fibers was 10–20, in zones of large diameter fibers less than 5.