Endoscopic Transcanal Infracochlear Vestibular Nerve Section with Hearing Preservation: A Pilot Cadaveric Study

Objective: Hearing preservation surgical approaches for the treatment of recalcitrant vertigo in Ménière’s disease remain elusive. The efficacy of endolymphatic sac decompression procedures have been called into question by randomized controlled trials. Vestibular nerve section procedures are effective; however, they necessitate a posterior fossa craniotomy and can carry significant morbidity. Transcanal endoscopic approaches to the internal auditory canal with cochlear preservation have been recently described and may offer a minimally invasive approach to sectioning the distal vestibular nerves while preserving hearing.

Study Design: Human cadaveric endoscopic dissection using real-time lateral skull base navigation with computed tomography (CT).

Methods: Three cadaveric human heads were imaged using CT with a skull base navigation protocol. Procedures were performed entirely through an intact pinna and external auditory canal using 0-, 30-, and 70-degree endoscopes (3 mm in diameter and 14 cm in length) and microsurgical drills. An infracochlear tunnel was defined by the cochlea superiorly, the internal carotid artery anteriorly, the jugular bulb inferiorly and facial nerve posteriorly. Once an internal auditory canalotomy was performed, the vestibular nerves were identified and sharply sectioned. Success of operation was confirmed via post-procedure CT and anatomic prosection of specimens.

Results: All specimens possessed adequate infracochlear tunnels to access the internal auditory canal on preoperative imaging. A large, intact superiorly based tympanomeatal flap was created. Transcanal, infracochlear work was performed while maintaining an intact ossicular chain and cochlea. An internal auditory canalotomy was performed using angled instruments and confirmed in real time via skull base navigation and by post-operative imaging. The vestibular nerves were easily identified and sectioned. The facial and cochlear nerves were identified and preserved. On postprocedure imaging, the cochlea did not appear violated.

Conclusion: A transcanal, infracochlear approach to the internal auditory canal may allow for a minimally invasive approach to vestibular nerve sectioning in patients with appropriate anatomy. This technique may provide more reliable outcomes than endolymphatic sac procedures and reduce operation related morbidity when compared with traditional posterior fossa approaches.