Simultaneous cochlear implantation during retrosigmoid resection of a large vestibular schwannoma under continuous electrically evoked auditory brainstem response monitoring.

Hearing preservation during surgery for large vestibular schwannomas (VS) remains challenging, and reports of simultaneous cochlear implantation (CI) via the retrosigmoid approach are exceedingly rare. We report, through close collaboration between neurosurgery and otolaryngology, what is, to our knowledge, the first case of simultaneous CI during retrosigmoid resection of a large sporadic VS under continuous intraoperative electrically evoked auditory brainstem response (EABR) monitoring. A 70-year-old woman with a 30-mm Koos grade 4 sporadic VS and contralateral profound hearing loss presented with right-sided scale-out audiometry (bilateral speech discrimination 0%). Retrosigmoid resection with continuous EABR monitoring via an intracochlear test electrode was performed, followed by immediate CI. Resection was terminated when wave V amplitude reached approximately 20% of baseline, achieving subtotal removal with preserved facial nerve function. The CI was activated postoperatively; aided thresholds reached 35-40 dB HL at 3 months, with stable tumor at 9 months. Preservation of EABR-not maximal tumor removal-should guide the extent of safe resection in CI-dependent candidates. Close interdisciplinary collaboration can extend hearing rehabilitation to patients with large VS, a population previously considered beyond the reach of hearing-preservation strategies.