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

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 nerve fibers, aiming to preserve both facial and cochlear nerve perineurium. The authors detail the key surgical steps of a modified- subperineurial dissection technique (MSPT), involving partial severing of the vestibular nerve of origin to identify the proper dissection plane for resecting a large VS via translabyrinthine approach (TLA). The goal was the anatomic preservation of the cochlear nerve and optimizing functional facial nerve results. The patient presented with a left-sided non-serviceable 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 MRI. The patient was considered a potential candidate for delayed hearing-rehabilitation device. Adopting subperineurial dissection could be challenging in larger tumor sizes due to difficulties with the residual capsule obscuring adjacent distorted anatomy. Therefore, in many cases of large tumors resected via the TLA, an extracapsular approach is frequently used, as cochlear nerve preservation isn't attempted. We find that in these instances, MSPT can be utilized to preserve the cochlear nerve integrity for possible future cochlear implantation, and still obtain a favorable extent of resection.