[Imaging of Cochlear Structures by Optical Coherence Tomography (OCT). Temporal bone experiments for an OCT-guided cochleostomy technique].

BACKGROUND: Optical Coherence Tomography (OCT) is a relatively new imaging technique, which provides scans similar to sonography on an optical base. We questioned whether OCT may be helpful in optimizing anatomical orientation in cochlear implant (CI) surgery. In a study on temporal bone specimens we tested, whether OCT provides information about the cochlear topography, particularly in situations, when for cochleostomy the bony otic capsule is already opened but the membranous endosteal layer is still intact.
MATERIAL AND METHODS: OCT was performed on five human temporal bone preparations, in which the cochleostomy was carried out still leaving the endosteum covering the fluid-filled inner ear intact. A prototype of operating microscope was used, in which a spectral-domain OCT (SD-OCT) with a central wavelength of 840 nm was integrated.
RESULTS: On all scans, OCT supplies information about inner ear structures, such as the lateral attachment of the basilar membrane dividing the scalae. Even delicate structures like the Reissner's membrane could be identified in one case.
CONCLUSIONS: This pilot study clearly documents the possibility to identify inner ear structures, especially the site of the scala tympani while its enveloping membranes are still intact. These findings may have an impact on cochlear implant surgery, especially as an orientation guide to localize the scala tympani precisely before opening the fluid-filled inner ear.