Retrolabyrinthine Approach for Hearing Preservation in Koos Grade II Vestibular Schwannoma - Surgical Nuances for Safe Gross-Total Resection: Surgical Video.

Introduction: The retrolabyrinthine approach is a valuable hearing-preservation technique for selected patients with small vestibular schwannomas and serviceable hearing. By preserving the otic capsule while providing a direct surgical corridor to the cerebellopontine angle and posterior aspect of the internal auditory canal, this approach may allow complete tumor removal with limited manipulation of the cerebellum and auditory structures. Careful patient selection, precise temporal bone drilling, meticulous microsurgical dissection, and continuous intraoperative neurophysiological monitoring are essential for optimizing functional outcomes. For the retrolabyrinthine approach, the retrolabyrinthine window—defined as the surgical corridor posterior to the labyrinth and anterior to the sigmoid sinus—should be made as wide as possible to maximize surgical exposure and working space Case Report: A 43-year-old man presented with a Koos grade II vestibular schwannoma and preserved serviceable hearing. Microsurgical gross-total resection was performed through a retrolabyrinthine approach with the patient in the supine position. Following mastoidectomy, the anatomical limits of the retrolabyrinthine corridor were carefully defined, preserving the semicircular canals and avoiding violation of the otic capsule. Adequate bone removal created a sufficiently wide surgical window to expose the posterior internal auditory canal and cerebellopontine angle while maintaining the integrity of the labyrinth. Continuous intraoperative neurophysiological monitoring was used throughout the procedure, including auditory brainstem responses (ABRs), facial motor evoked potentials (MEPs), and direct facial nerve stimulation. Progressive tumor debulking and meticulous microsurgical dissection were performed under high magnification, with particular attention to preservation of the arachnoid planes, cochlear nerve, facial nerve, and vascular supply to the auditory structures. The posterior internal auditory canal was adequately exposed without drilling the otic capsule, maximizing the possibility of hearing preservation. Gross-total tumor removal was achieved with anatomical and functional preservation of both the cochlear and facial nerves. Results: Postoperatively, the patient maintained serviceable hearing and demonstrated normal facial nerve function, corresponding to House-Brackmann grade I, without new neurological deficits. Conclusion: The retrolabyrinthine approach is an effective hearing-preservation option for carefully selected Koos grade II vestibular schwannomas. Creation of an adequately wide retrolabyrinthine corridor, preservation of the otic capsule, meticulous microsurgical dissection, and multimodal neurophysiological monitoring are fundamental for achieving gross-total resection while preserving cochlear and facial nerve function. This technique provides a good balance between tumor control and functional preservation in appropriately selected patients.