Obliteration of vestibular and cochlear aqueducts in animals.

The right vestibular aqueduct was obliterated in guinea pigs, chinchillas, and monkeys, and the right cochlear aqueduct and both the right vestibular and right cochlear aqueducts were obliterated in guinea pigs and chinchilas. Changes in auditory acuity were monitored by determining averaged temporal-response thresholds, and temporal-bone histologic studies were performed. Obliteration of the vestibular aqueduct or both the vestibular and cochlear aqueducts consistently produced endolymphatic hydrops in guinea pigs. In these animals, the auditory acuity gradually deteriorated. The low tones consistently were depressed more than the high tones. The auditory changes corresponded to the severity of endolymphatic hydrops. On the other hand, no significant histologic or audiometric changes were demonstrated in monkeys after obliteration of the vestibular aqueduct or in chinchillas after obliteration of the vestibular aqueduct or of both the vestibular and cochlear aqueducts. No significant histologic or audiometric changes were demonstrated in guinea pigs and chinchillas after obliteration of the cochlear aqueduct.