Modified Subperineurial Cochlear and Facial Nerve Preserving Technique via Translabyrinthine Approach: Nuances for Large Vestibular Schwannomas.

Abstract

The histologic composition of a vestibular schwannoma (VS) capsule includes residual nerve fibers and perineurium of the vestibular nerve of origin. Despite the perineurium being thin, an accurate subperineurial dissection plane can be established between the tumor parenchyma and residual vestibular nerve fibers, aiming to preserve both facial and cochlear nerve perineurium. We detail the key surgical steps of a modified subperineurial dissection technique, involving partial severing of the vestibular nerve of origin to identify the proper dissection plane for resecting a large VS via translabyrinthine approach. The goal was the anatomic preservation of the cochlear nerve and optimizing functional facial nerve results. The patient presented with left-sided nonserviceable hearing. A near-total resection was achieved through the technique, and facial and cochlear nerves were anatomically preserved. The postoperative course involved normal facial movement and a tiny residual tumor over the brainstem on magnetic resonance imaging. The patient was considered a potential candidate for delayed hearing rehabilitation device. Adopting subperineurial dissection could be challenging in larger tumor sizes because of difficulties with the residual capsule obscuring adjacent distorted anatomy. Therefore, in many cases of large tumors resected via the translabyrinthine approach, an extracapsular approach is frequently used, because cochlear nerve preservation is not attempted. We find that in these instances, the modified subperineurial dissection technique can be used to preserve the cochlear nerve integrity for possible future cochlear implantation, and still obtain a favorable extent of resection.