*3.2. Intraoperative Electrocochleography*

The results of intraoperative ECochG measurements are presented in Figure 8. The ECochG responses reflected the electro-mechanical activity of the inner ear on acoustic stimulation during the insertion of the electrode array into the cochlea. Ideally, the signal amplitude is expected to increase to some extent as the electrode array's most apical electrode contacts approach the cochlea's signal source. After bypassing the hair cells, which are probably responsible for the generated signal, the amplitude should gradually decrease with distance from this site. In fact, every movement of the electrode array can cause substantial disturbance in the micromechanical characteristic of the inner ear. Figure 8 shows the ECochG signal waveforms recorded for the two subjects who underwent CI surgery supported with the AIM system measurement. The observed changes in the amplitude of the ECochG signal are presumably results of electrode movement toward the cochlea, unintentional and unpredictable physical contact of the basilar membrane with the electrode array, slight movement of the robotic arm and surgeon's hand, as well as the implemented measurement technique. The maximum value of the recorded signal may vary for each subject. A credible ECochG response is considered to exceed 3 μV (internal noise of the implantable system does not exceed around 1 μV). The ECochG response was above the mentioned value after complete electrode insertion in both cases.
