Nerve fiber analysis and the aging process of the vestibulocochlear nerve.

Nerve fiber analyses were performed on the human vestibulocochlear nerve stained with Luxol fast blue-periodic acid-Schiff-hematoxylin with use of a combination of an image-analyzer and a computer. The axons were counted and their transverse (cross-sectional) areas were measured in 12 individuals. The average numbers of axons in each vestibular and cochlear nerve were 17,727 and 25,098, and the average transverse areas of their axons were 4.02 and 1.79 microns 2, respectively. Amyloid bodies and intervening Schwann cells in the vestibulocochlear nerve were also counted. The average number of amyloid bodies was 246 per transverse section of the nerve and their average size was 114 microns 2. The average number of intervening Schwann cells was 1,513. Our results indicated that the transverse axonal areas of the cochlear nerve became reduced with age, while the transverse areas of the amyloid bodies in the vestibulocochlear nerve increased with age. The number of vestibular nerve fibers did not seem to change with age.