Extended Retrosigmoid Craniotomy for Resection of a Cochlear Schwannoma.

Cochlear schwannomas are a rare subset of schwannomas arising from the cochlear nerve within the cochlea or internal auditory canal. These tumors can present with posterior displacement of the facial nerve, making facial nerve preservation a more technically demanding goal during surgery. This video describes a woman in her early 50s who presented with right-sided complete hearing loss and was thought to have a vestibular schwannoma extending into the internal auditory canal. Institutional review board approval was not required for this case report. Patient consent was obtained. The patient underwent a right extended retrosigmoid craniotomy. Intraoperatively, after cerebrospinal fluid release and cerebellopontine angle exposure, the tumor capsule was stimulated to identify the facial nerve. This early stimulation revealed the facial nerve was posteriorly displaced and splayed over the tumor's back wall. Dissection planes were developed superiorly and inferiorly along the nerve, allowing for careful central debulking of the tumor through these working windows. The facial nerve was identified in continuity from the brainstem, crossing under the cochlear nerve and adhering to the tumor's back wall. Because of the nerve's close adherence to the tumor, a thin layer of the tumor was left to protect the nerve. Postoperatively, the patient exhibited House-Brackmann grade 2 facial nerve function without new neurologic deficits. This case highlights key surgical techniques for schwannoma resection with posterior facial nerve displacement, emphasizing the importance of early facial nerve stimulation, meticulous debulking around the facial nerve using multiple dissection corridors, and careful balancing of complete resection with facial nerve preservation.