Outcomes of Cochlear Implantation After Vestibular Schwannoma Resection

Introduction: Vestibular schwannoma (VS) patients obtain auditory benefits from cochlear implantation (CI) simultaneously with surgical resection, or after a second-stage CI procedure. The CI provides binaural hearing in patients with preserved cochlear nerves. However, outcomes of CIs for VS patients remain highly variable even with an anatomically intact nerve.

Methods: This is a retrospective cohort single institution database study from the past 25 years evaluating hearing outcomes in patients with resected VS followed by CI insertion. Surgical outcomes, symptoms, and imaging data were evaluated. Auditory outcomes were collected including CI usage data, Consonant Nucleus Consonant (CNC) and Arizona Biomedical Sentence (AzBio) tests. Comparisons were done between groups including mean differences and correlations.

Results: 35 patients were included. The mean age was 56 years (SD: 12.3). 27 patients (77%) underwent translabyrinthine (TL) approach; 8 patients (22%) underwent a middle cranial fossa (MCF) approach. Patients presented mostly with single sided deafness (65%) and asymmetrical hearing loss (25%). The most common symptom was tinnitus (68%) followed by vertigo (65%). Tumors were mostly (80%) Koos grade 1-2 and 45% had a fundal cap on imaging. Median tumor volume was 0.40 cm3 for TL vs 0.17 cm3 for MCF (p=0.03). 19 patients (54%) underwent simultaneous CI and VS removal, and 7 patients (20%) did not obtain any auditory benefit from CI. Post-operative CNC was lower for TL than MCF (25% vs 46%;p=0.02), though there were no differences in AzBio (quiet or noise). Device use per day was 10.5 hours for TL and 10.07 hours for MCF (p=0.7). There was a positive correlation between CI usage with CNC (rho=0.4, p=0.0001) and AzBio in quiet (rho = 0.3, p=0.01).

Conclusions: After VS resection, most patients obtain auditory benefits from CI. There was a significant difference in auditory performance depending on the surgical approach used which can be influenced by tumor size. As expected, patients tend to perform better when using the device more frequently. Further multicenter studies need to be conducted to confirm these findings.