EFFECTS OF COMBINED RUPTURE OF REISSNERS MEMBRANE AND THE ROUND WINDOW ON HEARING IN THE GUINEA-PIG

Hearing impairment caused by sequential rupture of Reissner's membrane and the round window was investigated in guinea pigs to determine if the double-membrane break can cause acute profound sensorineural heari ng loss. Reissner's membrane was lacerated through the stria vasculari s at one of the turns of the cochlea, followed by rupture of the round window to create leakage of the perilymph. Action potentials (APs) to tone pip stimuli were recorded from the Fallopian canal electrode bef ore and 90 min after these procedures. The results showed that the ear s with the double-membrane break at the second turn showed a larger in crease in AP threshold than did the control ears with only round windo w rupture. However, this was not seen when Reissner's membrane had bee n ruptured at the other turns.