Use of Image-Guidance to Access the Endolymphatic Sac

Objective: One of the challenges in endolymphatic sac (ELS) decompression is the reliable identification of the ELS with minimal injury to surrounding structures. Here we propose to: 1) Demonstrate the feasibility of using imaging technology to identify the ELS. 2) Define a direct pathway from the lateral skull to the ELS. Method: The location of the ELS was approximated in a CT scan using its anatomic relationship to nearby structures, and a linear path was manually selected from the mastoid cortex to the predicted ELS. The path was visually verified to determine its relationship to the actual location of the ELS. Results: CT scans of 6 cadaveric temporal bones with bone-implanted fiducial markers were analyzed. The location of the ELS was predicted using traditional surgical landmarks. A custom Microtable (microstereotactic frame) was manufactured for each bone to target the ELS via a linear path (selected manually by CT). The bone was drilled to decompress the ELS. The Microtable was then mounted on the fiducial markers and the drill bit passed through its target hole to determine the actual targeted path. The drill bit coincided with the ELS in all specimens and did not transect any critical structures along its pathway. Conclusion: Current imaging technology allows for reliable identification of the ELS and generation of linear trajectories to reach the ELS without injury to adjacent structures. This work is the first step in the development of minimally invasive image-guided techniques to safely access the ELS in the treatment of Ménière’s disease.