Time-related changes in cochlear potentials in guinea pigs with experimentally induced endolymphatic hydrops.

In order to examine the changes in cochlear function occurring in hydropic ears over time, endolymphatic hydrops was provoked by obliterating the endolymphatic sac in 62 albino guinea pigs. Cochlear potentials (EP, CM, SP and AP) were recorded in the 1st, 2nd, 4th and 12th postoperative weeks, respectively. A significant reduction in the level of EP was already observed in the 2nd week and the potential was further suppressed by the 4th week. There was no significant difference between the levels of the 4th and 12th weeks. The amplitudes of CM and AP decreased progressively as time elapsed after the surgery. In sharp contrast to the other potentials, the abnormality in SP was most frequently observed in the 1st week. These results are discussed in the light of the available literature.