The inflammatory foreign body response (FBR) following cochlear implantation (CI) can negatively impact CI outcomes, including increased electrode impedances. This study aims to investigate the long-term efficacy of dexamethasone-eluting cochlear implant and locally delivered dexamethasone, a potent anti-inflammatory glucocorticoid, on the intracochlear FBR and electrical impedance post-implantation in a murine model. Preliminary impedance data in humans are also provided as a complement to the murine data to illustrate generalizability and reinforce implications related to clinical application. The left ears of CX3CR1+/GFP Thy1+/YFP (macrophage-neuron dual reporter) mice were implanted with dexamethasone-eluting cochlear implants (Dex-CI) or standard implant (Standard-CI) while the right ear served as unoperated control. Another group of dual reporter mice was implanted with a standard CI electrode array followed by injection of dexamethasone in the middle ear to mimic current clinical practice (Dex-local). Mouse implants were electrically stimulated with serial measurements of electrical impedance. Human subjects were implanted with either standard or Dex-CI followed by serial impedance measurements. Dex-CI reduced electrical impedance in the murine model and human subjects and inflammatory FBR in the murine model for an extended period. Dex-local in the murine model is ineffective for long-term reduction of FBR and electrode impedance. Our data suggests that dexamethasone-eluting arrays are more effective than the current clinical practice of locally applied dexamethasone in reducing FBR and electrical impedance.
Rahman et al. (2025) studied this question.