Objectives: To propose a remote, real-time, safe, and easy systematic method to determine electrode electric impedance components: access resistance, polarization capacitance, and polarization resistance. Patients: Patients who received a cochlear implant and had normal cochlear anatomy and complete array insertion were recruited. A total of four adult patients were included and separated in two groups according to implantation time. Intervention: Cochlear implant electrical impedance and its components were measured in all patients by using a novel diagnostic tool: a custom made software running in the patient's computer. Data is transmitted in real time to the investigator. Various stimulation and measuring strategies were used to obtain specific information in each cochlear region. Main Outcome Measures: Access resistance, polarization capacitance, and resistance of each patient were measured. Measurement success rate and required time for the patient were recorded. Results: Access resistance, polarization capacitance, and resistance were obtained in different modes, thus in every specific region of the cochlea. All measurements were successful. Each measurement took approximately 7 minutes and was transmitted in real time to the investigators. Conclusion: Routine use of this tool may allow constant assessment of cochlear health and could be eventually used to monitor the effect of drugs in the inner ear. This methodology provides an in vivo “electrical view” of the inside of the implanted cochlea.

Introduction: Cochlear implant (CI) impedance reflects the status of the electro neural interface, potentially acting as a biomarker for inner ear injury. Most impedance shifts are diagnosed retrospectively because they are only measured in clinical appointments, with unknown behavior between visits. Here we study the application and discuss the benefits of daily and remote impedance measures with software specifically designed for this purpose. Methods: We designed software to perform CI impedance measurements without the intervention of health personnel. Ten patients were recruited to self-measure impedance for 30 days at home, between CI surgery and activation. Data were transferred to a secured online server allowing remote monitoring. Results: Most subjects successfully performed measurements at home without supervision. Only a subset of measurements was missed due to lack of patient engagement. Data were successfully and securely transferred to the online server. No adverse events, pain, or discomfort was reported by participants. Discussion: This work overviews a flexible and highly configurable platform for self-measurement CI impedance. This novel approach simplifies the CI standard of care by reducing the number of clinical visits and by proving useful and constant information to CI clinicians.

As in any biophysical electrode-tissue environment, impedance measurement shows a complex relationship which reflects the electrical characteristics of the medium. In cochlear implants (CIs), which is mostly a stimulation-oriented device, the actual clinical approach only considers one arbitrary time-measure of the impedance. However, to determine the main electrical properties of the cochlear medium, the overall impedance and its subcomponents (i.e., access resistance and polarization impedance) should be described. We here characterized, validated and discussed a novel method to calculate impedance subcomponents based on CI measurement capabilities. With an electronic circuit of the cochlear electrode-tissue interface and its computational simulation, the access resistance and polarization impedance were modeled. Values of each electrical component were estimated through a custom-made pulse delivery routine and the acquisition of multiple data points. Using CI hardware, results fell within the electronic components nominal errors (± 10%). Considering the method's accuracy and reliability, it is readily available to be applied in research-clinical use. In the man-machine nature of the CI, this represents the basis to optimize the communication between a CI electrode and the spiral ganglion cells.

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 (false∼ 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 false∼ 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.

No abstract