Molded Round Window Niche Implant as a Local Long-Term Dexamethasone Delivery System in a Cochlear Implant-Trauma Animal Model

Background Preservation of residual hearing and reduction of fibrosis after cochlear implant (CI) surgery are pending issues to be resolved. The application of dexamethasone (DEX) has been proven to positively affect both. To deliver DEX in a long-term and precise way a round window niche implant (RNI) was developed, allowing drug diffusion via the round window membrane into the cochlea. Here first in vivo data are presented.

Methods Fourteen adult guinea pigs were randomly assigned to two groups (CI or CI+RNI group). All animals received a unilateral electrode insertion trauma followed by chronic CI insertion, the opposite ear served as control. The CI+RNI group was additionally implanted with a 10% DEX containing RNI. The RNIs were produced by micro injection molding, molds being 3D-printed based on a mean guinea pig niche model using digital light processing. Animals were followed up for 4 weeks. Hearing thresholds were measured, μCT-imaging and histology were performed.

Results The RNI fitted well into niche and μCT scans prove the CIs and RNIs still being in the correct position 28 days after implantation. The mean hearing threshold of the CI group significantly increased at 2, 4, 8, 16, and 40 kHz from day0 to day28, indicating that the electrode trauma was sufficient. Comparing the hearing threshold shift of CI and CI + RNI groups, no significant differences are observed. The amount of fibrosis in the basal turn was lower in the CI+RNI group than in the CI group.

Conclusion The 10%DEX containing RNIs were implantable and stayed in situ during the observation time. It has a protective effect against fibrotic response post-implantation. Future studies using variations of animal models, drugs and concentrations may result in even more promising effects on inner ear health.

This study was funded by the Federal Ministry of Education and Research of Germany (BMBF) project “RESPONSE–Partnership for Innovation in Implant Technology” in the program “Zwanzig20– Partnership for Innovation”, Project ID 03ZZ0928L.

Publication History

Article published online:
12 May 2023