Learning Objectives:

Background and Objective: Noninvasive middle and inner ear imaging using Optical Coherence-Tomography (OCT) presents some unique challenges for real-time, clinical use in animals and humans. OCT has been used in other fields for obtaining high-resolution cross-sectional images of the tissue. The goal of this study was to investigate whether OCT provides information about the middle and inner ear microstructures in both rats and mice by extratympanic approach.

Materials and Methods: Six BALB/c mice and Sprague Dawley rats were enrolled to the experiment, and to acquire an image of the entire tympanic membrane, the auricle and cartilaginous external auditory canal were removed, the swept-source OCT system was tested to identify the middle and inner ear microstructures. After that, the TM and bulla were removed to confirm whether more detailed middle and inner ear images might be obtained.

Results: It was possible to image through the tympanic membrane extratympanically and into the middle ear cavity involving several middle ear structures in both rats and mice. We could also obtain the inner ear images through the otic capsule and into the cochlea in the mice by extratympanic approach. However, the bulla should be removed to provide the inner ear structural images in the rats. The whole cochlea of the apical, middle and basal turn could be visualized and the bony thickness of the otic capsule covering the cochlea could also be measured simultaneously.

Conclusions: OCT is a promising technology to noninvasively assess middle ear and inner ear microanatomy in both mice and rats. These findings are meaningful because there were no previous report to describe the middle and inner ear structure looking by extratympanically. This imaging informations can be useful in the diagnosis of diseases of the middle and inner ear if it is clinically applied through further studies.