The transitional region of the eighth nerve in elderly humans: light and electron microscopic study.

To investigate the central-peripheral transitional region (TR) of the eighth nerve in elderly humans and to determine the reasons for its fragility, the eighth nerve root was studied by light and electron microscopy and by immunohistochemistry. Central and peripheral nervous tissue showed complex interdigitations at the TR. Slight proliferation of central glial tissue accompanied with disarranged course of the nerve fibers was also seen in this region. These findings were though to be age-related changes of the eight nerve. The capillaries ran in various directions at the TR and formed anastomoses with capillaries in the peripheral portion of the nerve. The density of capillaries in the peripheral nervous tissue was twice as high as that in the central nervous tissue. These findings indicated that the capillaries at the TR provide a connection between the blood supply to the central and peripheral portions of the eighth nerve. The occurrence of the age-related changes and complex course of the capillaries at the eighth nerve TR appeared to be related with the fragility of this region.