Flexible cochlear microendoscopy in the gerbil

Objectives/Hypothesis: To validate the scientific utility of flexible cochlear microendoscopy in the gerbil. This model is currently being developed to study the effects of intracochlear electrode positioning on functional parameters. Study Design: Animal experiments. Methods: A flexible fiberoptic microendoscope featuring a light channel and an outer diameter of 0.4 mm was specially modified to allow intracochlear visualization. Specifically, the focus distance was reduced to 1 mm and the optical properties were modified so that visualization was adequate when submerged in perilymphatic fluid. This endoscope was used to view intracochlear contents and monitor the progress of electrode insertions in 11 gerbils. The endoscopic data estimating the site of damage were compared to postmortem microdissections. Results: The endoscope allowed for adequate visualization of intracochlear content in all animals. The site of electrode contact seen in the endoscope was confirmed in the microdissected cochleae in 10 of 11 cases, indicating the endoscope's ability to correctly identify the site of intracochlear trauma in this animal model. Conclusions: The current report demonstrates the feasibility of intracochlear microendoscopy in an animal model of hearing preservation cochlear implantation.