Atraumatic surgical approaches to the vestibular labyrinth allowing for drug delivery, cochleo-vestibular implants, and other new surgical applications.

Introduction: Balance disorders are a major challenge today, as they greatly affect people's quality of life. Although medical treatment and vestibular rehabilitation are insufficient in many cases, significant improvements in the treatment of vestibular pathologies have been achieved in recent decades. New trends towards minimally invasive procedures have led to the study of direct treatment at the vestibular level, such as the use of vestibular implants. Great efforts have been made to acquire a thorough knowledge of these organs. However, the surgical anatomy and exact spatial orientation of the vestibular end organs, remain partially unknown. The aim of this study is to evaluate in three-dimensional (3D) reconstructions the feasibility of new minimally traumatic surgical approaches to the vestibule.

Methods: In order to plan and explore new surgical approaches to the vestibular end organs, a methodology based on 3D models of the inner ear has been developed. This methodology is tested on human temporal bones treated with vestibular implants to analyze possible new minimally traumatic approaches to the vestibular system. Pre- and post-implantation cone-beam computed tomography (CBCT) images were acquired. Image segmentation of the vestibular end organs was performed on the pre-implantation CBCT scan. An already validated, freely and openly available anatomical atlas of the inner ear, IE-Map, was used as a reference template for the anatomy. Alignment of the IE-Map with the CBCT images was achieved using the MATLAB image processing toolbox. Interactive 3D models were visualized with the non-commercial version of Dragonfly 2021.1 software.

Results: Image segmentation of the vestibular end organs and their 3D reconstructions were successfully performed in all cases. The 3D images showed reasonably realistic estimation of the location of the electrode within the vestibule and their relationships with respect to the different ampullary and otolithic receptors.

Conclusion: 3D reconstruction by segmentation of the inner ear with superposition of CT images and an anatomical model is feasible and offers valuable morphological insight into the complex anatomy of the inner ear. This technique is particularly useful for exploring potential new surgical approaches to access the vestibule and shows promising results in the context of future local drug delivery and/or direct electrical stimulation at the vestibular level. Three such approaches were proposed and preliminarily assessed.