Abstract
The short-term influence of round window membrane (RWM) rupture on cochlear potentials was investigated with special reference to the endocochlear DC potential (EP). The RWM of the guinea pig was incised with a needle or a glass micropipette without imposing pressure in the perilymphatic space, and the EP as well as the cochlear microphonics (CM) and compound action potentials (AP) of second cochlear turn were recorded before, during and after the operation.
While the EP suffered a moderate decline (about 36 mV in two hours) in five of ten animals, it showed little change in the remaining five animals. Changes of the CM and AP seemed parallel to that of the EP.
This study suggests that hearing loss can be caused by a tear of the RWM; however, such loss does not necessarily occur even in the presence of an obvious rupture. The reduction of the EP is likely to be responsible for the hearing loss in some cases of fresh RWM rupture. However, this hearing loss may not be severe, as demonstrated by the relatively small degree of reduction of cochlear potentials in this study.
