Cochlear implants (CI) are neuro-implants that replace the function of the inner ear in cases of profound deafness. Currently, more than 1,000,000 patients worldwide have such an implant. However, due to malpositioning and cell occupation, functionality can be significantly impaired, leading to reduced electrical stimulation efficiency and thus to a loss of implant function and thus hearing. Therefore, the aim of this project is to develop a new impedance spectrometric method to detect misplacements and cell occupations on CI stimulation electrodes.
Cochlear implants pose a special challenge because each inserted CI has an individual electrode geometry that must be taken into account. Therefore, the project aims to predict CI electrode geometry and position using CI electrode impedances so that no additional sensors are required. This method will allow monitoring the CI position during insertion and even during long-term use to understand possible loss of stimulation efficiency. By extending the frequency range and resolution towards impedance spectrometry, cell occupation on the CI electrodes can be detected and analysed. With a suitable mapping function and interpolation between simulated electrode impedances, the measured impedances and impedance spectra can be assigned to specific cell coatings and position parameters.
We have developed an impedance spectrometric measurement method that has been successfully tested with both enlarged CI models and commercial CI electrodes. We are also developing in vitro (suspension particles) and in silico (FEM) simulation models to detect cell occupancy around the CI electrodes and, in the future, to diagnose the cause of hearing deterioration in CI patients.