Ultrastructural pathology of the vestibule in patients with acoustic neurinomas: secondarily operated cases after posterior fossa operation.

The vestibular sensory epithelia from two patients with acoustic neurinomas were examined ultrastructurally. Both patients had first undergone posterior fossa operations 8 months and 3 years before residual tumors in the acoustic canals were removed by a secondary translabyrinthine operation. Labyrinthine sensory tissues were also removed for microscopic studies. In case 1, the utricular macula and the lateral and anterior cristae were observed, with all sensory epithelia showing fairly normal findings. Myelinated nerve fibers below the sensory epithelia also appeared normal. In case 2, only the utricular macula could be observed. The sensory epithelium showed severe degeneration, disappearing sensory cells and increasing cytoplasmic filaments of both the sensory cell and the supporting cell. Myelinated nerve fibers below the sensory epithelia were only rarely found.