Obliteration of vestibular and cochlear aqueducts in the guinea pig

Abstract

The study involved 42 healthy adult guinea pigs placed into two major groups. In group A, only histologic studies were performed after obliteration of the right vestibular aqueduct, the cochlear aqueduct, or both the vestibular and cochlear aqueducts. In group B, hearing changes were monitored by repeated determination of averaged temporal response thresholds after the same obliterative operations as in group A. At the conclusion of the experiments, histologic studies of temporal bone were performed and hearing changes were correlated with the severity of disease found in the inner ear. Histologic examination of 32 temporal bones from'animals in which the vestibular aqueduct or both the vestibular and cochlear aqueducts were obliterated consistently demonstrated endolymphatic hydrops. The endolymphatic hydrops was usually progressive, and its severity was proportional to the length of time from the operation. Serial determination of averaged temporal response thresholds in 18 guinea pigs after these operations demonstrated a progressive deterioration in thresholds. The hearing loss was greater at the lower frequencies. The audiometric changes correlated positively with the severity of endolymphatic hydrops. No significant audiometric or temporal bone histologic changes were found after obliteration of the cochlear aqueduct. © The American Laryngological, Rhinological and Otological Society, Inc.