Proefschrift_vd_Beek

electrode-neural interface has not been studied in detail. These effects are difficult to study because of a number of restraints (e.g., considerable variability in outcomes among patients and differences in human and animal anatomy). However, a large collection of outcome data can be acquired by studying patients implanted with different cochlear implant electrodes.

Figure 1: cadaveric temporal bone implanted with a cochlear implant. Clearly anatomic differences are seen in subsequent cochlear turns. Figure 1: cadaveric temporal bone implanted with a cochlear implant. Clearly anatomic differences are seen in subsequent cochlear turns.

Variations caused by factors other than the electrode-neural interface impede comparative studies. However, assessments of large numbers of implanted patients using the described techniques (e.g., ranking speech perception outcomes and, in particular, studying normalized or dB-converted T- levels) can provide useful information about the effectiveness of different aspects of the electrode- neural interface. Additionally, combining these data with clinically acquired CT information could provide great insight into the clinical effects of intracochlear positioning. When analyzing the intratympanic position of the electrode, one should focus on the distance to the neural elements not just in the medial-lateral plane but also in the perpendicular direction, that is, in the plane from the bottom of the scala tympani towards the osseous spiral lamina and the basilar membrane. Moreover, various other parameters that might influence the electrode neural interface (e.g., residual hearing, the etiology of deafness, fibrosis) can be studied by correlating those parameters with the clinically available stimulation levels along the array. Finally, outcome studies that analyze newly introduced electrode arrays will provide information about other aspects of electrode design. Combining those data with previously acquired data could elucidate the benefits and disadvantages of different aspects of electrode design. Thus, future electrode designs could retain their beneficial features and continue to improve their poor features.

7

143