Optimizing retrosigmoid approach for giant vestibular schwannoma resection: strategies and advances in surgical technique

Abstract: Vestibular schwannoma (VS), or acoustic neuroma, is a benign, well-encapsulated, slow growing nerve sheath tumor originating from Schwann cells forming the myelin sheath of the superior or inferior vestibular nerve. Grade IV VSs are large and giant (longitudinal diameter >3 cm), compress the brainstem and may displace the fourth ventricle, according to Koos’ classification. The mean size of tumors at diagnosis has gradually decreased over the years and is now 10–15 mm, with larger tumors being a minority due to improved diagnostic tools. The treatment of choice for giant VS is microsurgical resection—maximal safe tumor removal—with consideration of function preservation. Each case is managed on an individual basis, taking into account the unique characteristics of the patient’s condition. The surgical decision-making process involves consideration of various approach options, including retrosigmoid (more familiar for neurosurgeons, wide exposure to posterior fossa and facial nerve exit zone, possibility of hearing preservation, but it may require cerebellar retraction), translabyrinthine (non-hearing preservation approach, early exposure of internal auditory canal, does not require brain retraction), and subtemporal approaches (possible hearing preservation, for small schwannoma’s, limited brainstem exposure, temporal lobe retraction), each with its own indications and contraindications. Furthermore, the decision to pursue gross total resection or subtotal resection is typically made intraoperatively, after careful consideration of the tumor’s consistency and risk of injury for the surrounding neurovascular structures—specifically the facial nerve. In this article, we provide a comprehensive overview of the retrosigmoid approach for surgical resection of giant VSs. As a well-established and widely utilized technique, the retrosigmoid approach is familiar to most neurosurgeons. Indication, preparation, advances, tips, the pearls of every step, and expectations of the surgical resection.