Combined rupture of Reissner's membrane and round window: an experimental study in guinea pigs: experimental double-membrane rupture.
OBJECTIVE
Hearing loss caused by combined rupture of Reissner's membrane and the round window (RW) membrane (the double-membrane rupture) may differ depending on the site of the lesion on Reissner's membrane. The purpose of this experimental study was to reveal the relationship between the hearing impairment and the site of the lesion on Reissner's membrane.


BACKGROUND
According to experimental studies on perilymphatic fistula (PLF), profound hearing loss is not induced by rupture of RW alone, but by the double-membrane rupture. However, the mechanism responsible for hearing loss in the double-membrane rupture remains unclear.


METHODS
Compound action potentials (CAPs) of the cochlear nerve in response to tone pip stimuli (1, 2, 4, and 8 kHz) were recorded before the lesion, 90 minutes after the Reissner's membrane rupture, and 90 minutes after subsequent laceration of the RW. Reissner's membrane was ruptured at one of the four turns for comparison.


RESULTS
The double-membrane rupture caused a more severe increase in CAP thresholds than seen with separate ruptures, when the Reissner's membrane was ruptured at the second turn. Such pronounced increase in threshold was not seen in ears with the rupture at other turns.


CONCLUSIONS
The double-membrane rupture causes varying degrees of hearing loss depending on the site of the lesion of Reissner's membrane. When the Reissner's membrane was ruptured at the second turn, the most severe hearing loss was detected.
Kobayashi
T
T
Department of Otolaryngology, Ehime University School of Medicine, Japan.
Gyo
K
K
Yanagihara
N
N
D000818:Animals; D001300:Audiometry, Evoked Response; D001489:Basilar Membrane / Q000293:injuries* / Q000473:pathology*; D004195:Disease Models, Animal; D005072:Evoked Potentials, Auditory; D005402:Fistula / Q000473:pathology; D006168:Guinea Pigs; D006319:Hearing Loss, Sensorineural / Q000175:diagnosis / Q000209:etiology; D010498:Perilymph; D012405:Round Window, Ear / Q000293:injuries* / Q000473:pathology*; D012421:Rupture / Q000473:pathology; D012720:Severity of Illness Index; D000159:Vestibulocochlear Nerve / Q000502:physiology