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 perilymphatic fistula. Three groups of guinea pigs included 1) 10 normal control animals, 2) 10 experimental animals with induced perilymphatic fistula, and 3) 10 control animals with induced perilymphatic fistula. In the first two groups, animals were successively tested in three positions: 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 potential (SP) amplitude, action potential (AP) amplitude, and AP threshold for the click stimuli. Only the normal control group showed a significant effect of body position for the SP/AP amplitude ratio. Average change was greater in the experimental group, but high variability precluded statistical significance. Both fistulized animal groups exhibited high variability in the SP/AP amplitude ratio, with and without postural change. The SP/AP amplitude ratio and SP amplitude were significantly larger for the two fistulized groups than for the normal control group. No significant change in threshold occurred across positions for any group.