Quantitative analysis of glia in the facial and vestibulocochlear nerves

Human normal vestibulocochlear and facial nerve trunks were cut off near the brain stem of the individuals who ages ranged from 24 to 93 years old. For this study, the discriminative staining method (Luxol fast blue--periodic acid-Shiff--hematoxylin triple stain) was adopted. It is admitted that the vestibulocochlear nerve medial to the internal auditory canal histologically resembles to the central nervous system in the rat. In order to confirm the fact in human, the intervening glial cells among nerve fibers were observed in the transverse section of vestibulocochlear and facial nerves. Schwann cells and microglia were observed among nerve fibers, but oligodendroglia. And the number of the glia was counted. The glial ratios related to the transverse nerve areas and the number of axons were calculated, and were examined in relation to aging. We found that there were more Schwann cells than microglia on both vestibulocochlear and facial nerves, facial nerve had more Schwann cells than vestibulocochlear nerve, and the number of Schwann cells per single myelinated fiber increased with age in the facial nerve. A quantitative study has not been included in the literature on the number of glia in the peripheral nervous system. Then, a quantitative study of human normal glial may be essential to elucidate pathogenesis regarding peripheral neuropathies, nerve injury or nerve sheath tumors as distinguished from the normal aging process.