Partial labyrinthectomy with hearing preservation: an experimental study in guinea pigs.

Recent advances in neurotologic surgery have challenged the traditional belief that violating the labyrinth is incompatible with hearing. Our aim in this study was to define the conditions that result in hearing preservation and hearing loss after surgery on the labyrinth. A guinea pig model was developed. Click-evoked auditory brain stem responses were used to determine hearing thresholds. Animals underwent surgical destruction of part or all of the vestibular labyrinth. Transection and plugging of the lateral semicircular canal resulted in normal hearing. Transection of multiple semicircular canals also resulted in hearing preservation. Intentional suctioning of perilymph from a transected canal led to transient hearing loss with complete recovery. Sequential destruction of the entire lateral semicircular canal resulted in preserved hearing as long as the vestibule was not opened. Wide vestibulotomy resulted in hearing loss. Preliminary histologic studies showed that cochlear hair cells were preserved in most cases. The results of our experiments demonstrate the feasibility of preservation of hearing after partial labyrinthectomy and provide physiologic criteria for developing new operations on the inner ear in human subjects.