Extrusion of corpora amylacea from the marginal glia at the vestibular root entry zone

We have studied the vestibular nerve in patients suffering from Meniere's disease and vascular cross-compression syndrome of the root entry zone due to close contact with the nerve of the antero-inferior cerebellar artery or one of its branches. All patients underwent vestibular neurectomy using the restrosigmoid approach which allows the resection of a relatively long nerve segment. In all the studied vestibular nerves a central and a peripheral zone could be distinguished. In the central zone, a massive accumulation of corpora amylacea (CA) was detected in the cytoplasm of astrocytes. Many CA were seen to protrude from the central nervous system into the pial connective tissue. These structures resembled sessile or pedunculated polyps, with a complex system of scissurae at their bases. CA were also found in extracellular location in the pial connective tissue near capillaries, and not wrapped by membranes. Our findings suggest that after their production in astrocytes, CA are transferred into the pial connective tissue across the glial-limiting lamina. Thus, the present results indicate that CA do not merely represent an accumulation of abnormal material, but they could instead be part of a glio-pial system devoted to the clearance of substances from the nervous system.