Electrocochleography of ears with mumps deafness.

Electrocochleography was performed on 16 affected ears of 15 deaf patients whose deafness had resulted from the mumps. Although pure-tone audiometry showed no response in each case, the cases of mumps deafness can be classified into the following three types of cochlear impairment according to the cochlear microphonic (CM) response: (1) no action potential (AP) response but a well-developed CM response, with impairment at the neural level and probable functioning of Corti's organ; (2) absence of both the AP CM responses, with severe impairment of both the neural regions and Corti's organ; (3) no AP response but a decreased CM response, with severe impairment of the neural regions and partial impairment of Corti's organ.