EXTRUSION OF CORPORA-AMYLACEA FROM THE MARGINAL GLIA AT THE VESTIBULAR ROOT ENTRY ZONE

We have studied the vestibular nerve in patients suffering from Menier e's disease and vascular cross-compression syndrome of the root entry zone due to close contact with the nerve of the antero-inferior cerebe llar 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 ner ves a central and a peripheral zone could be distinguished. In the cen tral zone, a massive accumulation of corpora amylacea (CA) was detecte d in the cytoplasm of astrocytes. Many CA were seen to protrude from t he central nervous system into the pial connective tissue. These struc tures resembled sessile or pedunculated polyps, with a complex system of scissurae at their bases. CA were also found in extracellular locat ion in the pial connective tissue near capillaries, and not wrapped by membranes. Our findings suggest that after their production in astroc ytes, CA are transferred into the pial connective tissue across the gl ial-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 sub stances from the nervous system.