Intracochlear Drug Delivery Using a Catheter and Dexamethasone-Eluting Electrode Preserves Residual Hearing Post-Cochlear Implantation.

Abstract

Objectives: This study aims to assess the feasibility and safety of a cochlear catheter (cannula) for inner ear drug delivery during cochlear implantation. We evaluated the otoprotective effect of L-N-acetylcysteine (L-NAC) administered via a cannula in combination with a dexamethasone-eluting cochlear implant (CI).

Study design: An animal model study.

Setting: Animal facility of an academic institution.

Methods: Animals were divided into 8 groups: (1) implantation with a CI; (2) implantation with a dexamethasone-eluting CI (CIDexel); (3) cannula injection of artificial perilymph (Can+AP); (4) cannula injection of Ringer (Can+R); (5) cannula injection of R and CI (Can+CI); (6) cannula injection of R and Dexel (Can+Dexel); (7) cannula injection of 2 mM L-NAC and CI (Can L-NAC 2 mM+CI); or (8) cannula injection of 2mM L-NAC and Dexel (Can L-NAC 2 mM++Dexel). The contralateral ear served as the control group. Hearing thresholds were determined preoperatively, and at postoperative day (POD 7) and POD 30 post-cochlear implantation, using auditory brainstem responses (ABRs). The organ of Corti dissections were performed at POD 30 for hair cell (HC) viability, and oxidative stress assessment using immunostaining.

Results: The L-NAC (2 mM) and dexamethasone-eluting electrode group had significantly lower hearing thresholds than the standard CI, Can L-NAC 2 mM, and Dexel groups. The animal group treated with L-NAC (2 mM) and dexamethasone-eluting electrode showed higher HC viability and reduced oxidative stress.

Conclusion: An intracochlear cannula can deliver pharmaceutical interventions without causing additional hearing loss. L-NAC presents strong anti-apoptotic potential and administration through a cannula together with Dexel implantation, and achieves a synergistic effect enhancing the otoprotection.