Electrocochleography and cochlear pathology.

In experimentally damaged inner ears the structural alterations were correlated to electrocochleographic responses of the ear. Sectioning of the cochlear nerve with degeneration of the type I neurons but intact sensory cells results in normal cochlear microphonics but very weak and atypical nerve responses. By contrast, damage of the organ of Corti with retrograde degeneration abolished primarily the cochlear microphonics, whereas the compound VIII nerve action potential is barely affected when only the outer hair cells are gone and even a small number of surviving inner hair cells is still compatible with a relatively strong compound action potential of the cochlear nerve.