Biological Response Dynamics to Cochlear Implantation: Modeling and Modulating the Electrode-Tissue Interface

Objective: The present study primarily aims to study and model the impedance dynamics following cochlear implant (CI) surgery in humans. Secondarily, to observe how the modulation of a single-dose topic dexamethasone alters this response. Design: CI impedance and impedance subcomponents were measured in a day-by-day basis between CI surgery and its activation (∼ 1 month). Impedance dynamics were mathematically modeled. Furthermore, we conducted a randomized double-blind placebo-controlled clinical trial to evaluate the effect of dexamethasone application. Results: The model showed good fitting for all impedance's measures and both modulations over time. The clinical impedance and impedance subcomponents showed different patterns between groups during the first week postimplantation. Single-dose topical dexamethasone had a transient effect on Impedances, postponing (for ∼ 3 days) but not preventing the rise in impedance and its application was mainly effective at the base of the cochlea. Conclusions: The proposed mathematical fitting properly resembles the impedance dynamics in humans and their modulation due to the dexamethasone. The impedance subcomponents' dynamic pattern showed a time-course consistent with the biological processes of the foreign body reaction. Single-dose topic dexamethasone has a temporal reduction effect in impedance values on the basal turn of the cochlea but does not prevent the rise on the long-term.