Source
Department of Otolaryngology, Head & Neck Surgery, Johns Hopkins University School of Medicine, Baltimore, MD 21205, USA.
Abstract
CONCLUSION:
Implantation of vestibular prosthesis electrodes in chinchilla semicircular canal ampullae can be accomplished without significant loss of cochlear function; however, the risk of hearing loss with the current surgical technique is high.
OBJECTIVES:
To determine if it is possible to implant vestibular prosthesis electrodes into the labyrinth without damaging hearing, and to quantify the extent of hearing loss due to implantation.
MATERIALS AND METHODS:
The left semicircular canals of six chinchillas were implanted with three bipolar pairs of electrodes using a transmastoid approach. Right ears, which served as controls, were subjected to the same mastoid approach without fenestration and implantation. Auditory brainstem response hearing thresholds to free-field clicks and tone pips at 2, 4, 6, and 8 kHz were measured bilaterally 3-9 weeks after implantation. Hearing thresholds were compared between sides and against data from six normal chinchillas.
RESULTS:
Four implanted ears suffered severe hearing loss, with thresholds ranging from 5 to 11 SD above the mean threshold of sham surgery control ears across all tested stimuli. Two implanted ears had preserved hearing, with thresholds remaining within 1 SD of the mean threshold of sham surgery control ears across nearly all stimulus frequencies.