IN-VIVO COCHLEOSCOPY THROUGH THE ROUND WI NDOW

The overall aim of the present investigation was to develop a techniqu e for endoscopic investigation of the cochlea. In the experiments repo rted here, the possible effect of the endoscope - called the ''cochleo scope'' - on the electrophysiology of the cochlea was investigated by recording the cochlear action potential (CAP) threshold tuning curve f rom (0.1-34 kHz). The dorsolateral bulla of anesthesized guinea pigs ( with ketamine 60 mg/kg and Rompun 12 mg/kg) was opened, after which th e cochleoscope was introduced under micromanipulator control through t he round window membrane. Three cochleoscopes were used and had diamet ers of 0.29 mm, 0.7 mm and 0.89 mm, respectively, containing 2000, 300 0 and 3000 fibers each. Experiments in 7 animals showed that the cochl eoscope did not influence CAP thresholds. Although the present resolut ion of the endoscopes is limited,the basilar membrane can be clearly d istinguished from the osseous spiral lamina. It is anticipated that im proved resolution will allow the cochleoscope to be used for diagnosti c purposes in cases of sensorineural hearing loss.