Temporal bone histopathology in deafness due to cryptococcal meningitis.

This paper reports on a patient who survived an attack of cryptococcal meningitis eight years prior to his death. A bilateral sensorineural hearing loss had been noted a short time before the patient was admitted to the hospital, and was the only complication after he recovered from the disease. Histopathologic study of the temporal bones showed a similar pattern of pathology in both ears, the most striking finding being a severe loss of spiral ganglion cells in Rosenthal's canal, and of cochlear nerve fibers in the osseous spiral lamina and internal auditory meatus. The vestibular nerve was mostly free from pathology. The organ of Corti was atrophic but the hair cell population appeared to be almost normal. A slight number of cryptococci were observed in limited areas of the cochlear and the saccular nerves in the internal auditory meatus. The severe pathology of the cochlear nerve was compatible with audiologic evaluations, which pointed to a retrocochlear lesion. Thus, this case demonstrates some characteristic aspects of cryptococcal infection of the temporal bone: The primary site of invasion was the cochlear nerve in the internal auditory meatus and the modiolus, leading to the loss of ganglion cells and nerve fibers, while the vestibular nerve appears to have been resistant to infection.