ELECTROCOCHLEOGRAPHY WITH POSTURAL CHANGES IN PERILYMPHATIC FISTULA -ANIMAL STUDIES

The present study investigated the effect of altering body position on electrocochleographic findings in the presence and absence of perilym phatic fistula. Three groups of guinea pigs included 1) 10 normal cont rol animals, 2) 10 experimental animals with induced perilymphatic fis tula, and 3) 10 control animals with induced perilymphatic fistula. In the first two groups, animals were successively tested in three posit ions: first with the ventral aspect down, again after 30 minutes with the test ear up, and again after 15 minutes with the test ear down. In the third group, body position was not altered. Stimuli consisted of clicks and 6,000-Hz tone bursts. Data analysis included summating pote ntial (SP) amplitude, action potential (AP) amplitude, and AP threshol d for the click stimuli. Only the normal control group showed a signif icant effect of body position for the SP/AP amplitude ratio. Average c hange was greater in the experimental group, but high variability prec luded statistical significance. Both fistulized animal groups exhibite d high variability in the SP/AP amplitude ratio, with and without post ural change. The SP/AP amplitude ratio and SP amplitude were significa ntly larger for the two fistulized groups than for the normal control group. No significant change in threshold occurred across positions fo r any group.