Effects of combined rupture of Reissner's 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 hearing loss. Reissner's membrane was lacerated through the stria vascularis 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 before and 90 min after these procedures. The results showed that the ears with the double-membrane break at the second turn showed a larger increase in AP threshold than did the control ears with only round window rupture. However, this was not seen when Reissner's membrane had been ruptured at the other turns.