Changes in CAP adaptation in experimentally induced endolymphatic hydrops

Objective: To determine the effect of experimentally induced endolymphatic hydrops (ELHs) on compound action potential (CAP) adaptation. Methods: The CAP was recorded 1 month after surgical treatment to produce ELH. The CAP threshold in response to click stimuli showed no significant differences between the hydropic and control groups. The CAP was elicited from the retroauricular-exposed round window using a silver ball electrode. Click trains consisting of 10 clicks with an interclick interval (Δt) of either 4 or 8 ms were delivered through a loudspeaker placed in front of the animalsʹ ears. The patterns of adaptation to these click trains were evaluated as functions of Δt and intensity level. Results: An abnormal pattern of CAP adaptation was observed in hydropic ears. Conclusions: These findings suggest that early ELH influences CAP adaptation.