Cochlear endoscopy with preservation of hearing in guinea pigs.

Advances in fiberoptic technology have revolutionized the way many disorders are treated by otolaryngologists. We have previously described our experiences with cochlear endoscopy during cochlear implantation. However, endoscopy of the functioning cochlea has not previously been reported. To test the hypothesis that endoscopy of the guinea pig cochlea is possible without catastrophic loss of auditory function, we subjected 20 ears of 10 Hartley-strain albino guinea pigs to limited endoscopy of the cochlea through the round window with evaluation of distortion product otoacoustic emissions and auditory brain stem responses. Insertion of the endoscope caused measurable changes in auditory brain stem response latency and amplitude. Distortion product otoacoustic emission amplitudes were reduced an average of 6 dB with greater loss close to the round window. Frequencies above 18 kHz, corresponding to the region of endoscopy, were not evaluated in this preliminary study and are suspected to have sustained more damage. Results demonstrate that endoscopy of the guinea pig cochlea is possible without major loss of the above physiologic measures in the regions tested. If endoscopy of the cochlea is to become a tool with clinical and basic science applications, refinements in techniques to avoid damage are necessary.