Electrocochleography in Guinea Pigs with Experimental Endolymphatic Hydrops

Abstract

In this study we attempt to determine whether the dominant negative summating potential (DNSP) is present during the earlier stages of induced hydrops development. Electrocohleographs (ECoG) were taken 3 days, 4 days, 1 week, 2 weeks, 3 weeks, and 10-20 weeks after obliteration of the endolymphatic sac in guinea pigs with electrodes in the basal turn scala vestibuli.The action potential (AP) thresholds rose and the AP amplitudes decreased with time following surgery. The increases in the summative potential (SP) amplitudes and in the rises in the SP/AP ratios at 95 dB pe SPL in response to clicks tended to be greater 3 and 4 days postoperatively than subsequently. These results indicate that the potential for DNSP exists during the early stages of endolymphatic hydrops formation, before the hydrops is fully developed.