Microsurgical Gross Total Resection of an Intracanalicular-Cisternal (Koos-4) Vestibular Schwannoma via a Retrosigmoid Approach with Intraoperative Endoscopic Assistance.

We present the case of a 23-year-old female with a history of progressive hearing loss in the left ear, dizziness, and vertigo. Magnetic resonance imaging demonstrated a left mass extending from the internal auditory canal into the cerebellopontine angle (Koos-4). ¹ A retrosigmoid approach assisted with a microinspection tool was chosen. ^2-5 Microsurgical near total resection was achieved. The patient presented a postoperative facial deficit (House-Brackman grade 2 postoperative), with complete resolution after 2 months. Video 1 highlights the critical steps of the retrosigmoid approach and the benefit of using the microinspection tool for vestibular schwannoma resection.
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