Nerve Fiber Arrangement of Human Facial Nerve within Temporal Bone

Abstract

This paper describes the scanning electron microscopic appearance of nerve fibers and nerve fiber bundles in the human facial nerve within the temporal bone. The facial nerve used in the present study was obtained from the temporal bone removed at autopsy. To examine the fine morphology of the nerve, a modification of Evan's tissue digestion method was used to remove the extracellular material around the nerve fibers.1. The fine morphology of the nerve fiber and fiber bundles was clearly visible.2. The nerve did not run as a single bundle through the temopral canal. Several anastomoses and bifurcations were seen.3. The arrangement of the bundle was complicated, and branches of the bundle changed their courses in the deep portion.4. The arrangement of nerve fibers was also complicated. In areas of anastomosis, adjacent nerve fiber bundles did not only join to form one bundle, but nerve fibers also intermingled with each other.These findings suggest that the arrangement of nerve fibers and nerve bundles is very complicated. It is generally accepted that the facial motor nucleus has a somatotopic organization. However, the spatial arrangement of nerve fibers within the temporal canal is controversial. The present findings suggest that there is no spatial arrangement and that nerve fibers are diffusely arranged.