A Safe Technique for Transposing the Facial Nerve in the Transcochlear Approach

Objective: The tortuous course of the facial nerve makes it susceptible to iatrogenic injury. Posterior rerouting of the facial nerve provides maximum exposure but has a higher risk of postoperative nerve palsy. We demonstrate a safe technique for posterior rerouting of the facial nerve in the transcochlear approach. Study Design, Material, and Methods: Initial mastoidectomy, facial nerve dissection, and skeletonization of the internal auditory canal were performed on five preserved cadaveric heads (10 sides) and in 10 clinical cases. To avoid drilling on the vascularized lateral surface of the nerve, bone surrounding the nerve was drilled anteriorly and posteriorly, leaving a 2 mm bony covering. The remaining bone was detached and elevated inferior-superiorly. The chorda tympani were transected, the tympanic portion of the facial nerve was skeletonized to the geniculate ganglion, and the greater superficial petrosal nerve was sectioned. A dural opening was made over the internal auditory canal and the facial nerve was separated from the vestibulocochlear complex. Results: The facial nerve was reflected out of its position in the internal auditory and fallopian canals and transposed posteriorly. Cranial nerves V, VII, IX, X, and XI as well as the clivus, bilateral vertebral arteries, and the basilar artery were observed. Conclusions: Drilling along the anterior and posterior aspects of the nerve destabilized it while mitigating the risk of vascular or thermal injury.