Prolongation of the cochlear microphonic in man. Cochlear microphonic ringing.

During routine extra-tympanic electrocochleographic (ECochG) recording we have observed that in many cases more cycles are seen in the cochlear microphonic (CM) recording than are present in the acoustic stimulus. We have termed this phenomenon CM 'ringing'. Ringing is present in 69% of our normal subjects and in 43% of patients with deafness of different aetiologies. In the cochlear and Ménière subgroups those cases showing ringing have a significantly larger CM amplitude (p less than 0.001 and p less than 0.01 respectively). The possible origin of this phenomenon is discussed.