P11 - Detecting Cell Growth on Cochlear Implant Stimulation Electrodes by Impedance Spectrometry

16. Dresdner Sensor-Symposium 2022
2022-12-05 - 2022-12-07
(Bio-)Medizinische Sensorik
M. Sehlmeyer, H. Hitzemann, C. Thoben, S. Zimmermann - Leibniz University Hannover, Hannover /D, M. Bhavsar, H. Maier - Hannover Medical School, Hannover/D
105 - 108


The most important way of communication between people is still speaking and hearing. If a person is deaf, this significantly limits his or her ability to communicate. However, if the patient's auditory nerve is still intact and the reason for deafness is damage to the hair cells, a cochlear implant (CI) can bypass them. Thus, the patient gets the possibility to hear again, which can increase the quality of life. Cochlear implants are hearing prostheses used to replace the function of the inner ear. In simplified terms, a CI consists of an external part on the outside of the head and an internal part in the patient's inner ear. An external speech processor records sounds from the environment, converts them into electrical signals, and then transmits them to an electrode array located inside the cochlea in the perilymph-filled scala tympani. Inside the cochlea, the stimulation electrodes of the CI stimulate the spiral ganglion cells of the auditory nerve electrically. The functionality of a CI strongly depends on the current that stimulates the spiral ganglion cells, which in turn strongly depends on the electromagnetic properties of the surrounding tissue. A well-known issue of CIs is the growth of cells such as fibrocytes or blood contamination from a damage of the cochlea wall on the stimulation electrodes. When cells grow on the stimulation electrodes, thereby changing the dielectric constant, they weaken the electric field at the auditory nerve and the impedance increases as Bester et al. showed in. Thus, stimulation efficiency of the CI decreases and the patient’s ability to hear deteriorates. However, the degradation of a patient's hearing can also have other reasons, such as an incorrect position of the CI inside the cochlea or a tip fold-over during insertion. In case of a degradation of the hearing ability of a patient with CIs, it is important to know the cause at an early stage in order to intervene with an individual treatment. One method to detect cell growth on the stimulation electrodes at an early stage and to differentiate cell growth from other influencing effects is recording the impedance spectra of CI stimulation electrodes.