MYELIN-CONTAINING CORPORA-AMYLACEA IN VESTIBULAR ROOT ENTRY ZONE

The vestibular nerve of patients with Meniere's disease and vascular c ross-compression syndrome of the root entry zone due to the antero-inf erior cerebellar artery was studied. All patients underwent vestibular neurectomy using the retrosigmoid approach, which permits the removal of a long nerve segment. CA were found in the cytoplasm of astrocytes that had not shown signs of degeneration at the central portion of th e vestibular root entry zone. No membrane intervened between CA and th e surrounding cytoplasm, which was rich in filaments, in particular ne ar the CA, and poorly equipped with other organelles. CA were round or oval inclusions measuring 10-12 mu m in diameter. The matrix of the C A was composed of low-density amorphous material, with irregular masse s displaying a medium density. A network of randomly oriented filament s and bilaminar, osmiophilic lipid fragments with the same structure a nd thickness of myelin layers were embedded in the matrix. The CA rich in bilaminar fragments were recognizable also at low magnification fo r their high electron density. In the astrocytic cytoplasm, near the C A, round or oval-shaped, electron-dense bodies with a multilamellar st ructure were often visible. These results confirm the hypothesis that CA may contain degenerating myelin embedded in a microenvironment rich in glucose polymers and that CA could be an indicator of neurodegener ation.