Impact of Intratympanic Gentamicin on Cochlear Implant Outcomes

Intratympanic gentamicin (ITG) instillation is a therapeutic option in advanced Menière's disease (MD) to control vertigo. ITG aims to induce vestibular hypofunction by selective ablation of vestibular hair cells. However, it may also adversely affect cochlear hair cells and the neural auditory pathway. Preservation of the neural auditory pathway is critical, as today cochlear implantation (CI) is the gold standard for auditory rehabilitation in patients with MD. This study assesses the impact of prior ITG treatment on CI outcomes in patients with MD.

This retrospective cohort study included 36 CI recipients with MD. Patients were divided into two groups: ITG (n = 14) and Control (n = 22). Primary outcome measure was the CI-aided Freiburg monosyllabic words test at 65 dB SPL (WRS65[CI]) at follow-up visits T1 (0-3 months), T2 (3-6 months), and T3 (≥6 months).

Both groups showed significant improvements in aided WRS65 over time, with the ITG group exhibiting inferior outcomes compared to the control group (relative treatment effect [RTE] 0.38 [ITG] versus 0.57 [control]; p < 0.001). Post hoc analysis confirmed between-group differences in WRS65[CI] outcomes at all follow-up visits (T1: median 30% versus 46%, p = 0.012; T2: 40% versus 60%, p = 0.009; T3: 57.5% versus 72.5%, p = 0.027; ITG versus control group, respectively). A linear mixed-effects model demonstrated that ITG treatment was associated with lower WRS65[CI] outcomes (β = -18.85, p = 0.014), while other preimplantation hearing test results and age at implantation did not show significant effects on the outcome.

ITG treatment was associated with worse CI outcomes in MD patients. We recommend that patients should be counseled regarding the potential adverse effects of ITG on the neural auditory pathway that may lead to inferior CI outcomes.