Light and electron microscopic investigation of cochlear nerve specimens from profoundly deaf patients.

Surgical specimens of cochlear nerves from patients suffering from sudden deafness or congenital deafness have been evaluated with regard to the number of nerve fibres and the morphological appearance. The meatal segment of cochlear nerves from 6 patients with sudden deafness shows a variable number of nerve fibres and different morphological changes. The duration of deafness does not correlate with the number of nerve fibres. In the case of congenital deafness for more than 17 years the cochlear nerve presented an apparently normal number of myelinated fibres. The presented study reveals that the retrograde degeneration of the human cochlear nerve is unpredictable.