Impedances of Cochlear Implant Electrodes

Objective: The current study investigateswhether, during a Cochlear Implant (CI) surgery, conditioning(i.e. applying short bursts of electrical stimulation)within a saline solution can have positive effects on subsequentintra-operative measurements. We hypothesize that,based on previous research, the impedance values will bereduced, and that the reproducibility of Electrically EvokedCompound Action Potentials (ECAPs) is improved as aresult of conditioning.Methods: We conditioned half of the electrode contacts,within a saline solution, before CI insertion, using 23 MEDELimplants. Impedance was measured for both the conditionedand non-conditioned groups at five time points.Repeated ECAP recordings were measured and comparedbetween the conditioned and non-conditioned groups.Results: Impedance of the electrode contacts were reducedby 31% after conditioning in saline solution; however,there were no clinically relevant differences afterthe implantation of the electrode array. The hypothesisthat measurement reproducibility would be increased afterconditioning could not be confirmed with our data.Within the saline solution, we observed that 44% of theelectrode contacts were covered with air bubbles, whichmost disappeared after implantation. However, these airbubbles limited the effectiveness of the conditioning withinthe saline solution. Lastly, the effect of conditioning on thereference electrode stimulation was approximately 16% ofthe total reduction in impedance.Conclusion: Our data does not suggest that intraoperativeconditioning is clinically required for cochlear implantationwith MED-EL implants. Additionally, an in-vivo ECAPrecording can be considered as a method of conditioningthe electrode contacts.Significance: We confirm that the common clinical practicedoes not need to be changed.

本研究旨在探讨在耳蜗植入术（CI）过程中，于生理盐水中进行条件化处理（即施加短时脉冲电刺激）是否会对后续术中测量产生积极影响。基于前期研究，我们假设阻抗值将有所降低，且经条件化处理后，电诱发电位（ECAPs）的可重复性将得到提升。研究方法：我们使用23 MEDEL植入器，对电极接触的一半进行条件化处理，并在耳蜗植入前在生理盐水中进行。对条件化与非条件化两组在五个时间点进行了阻抗测量，并对比了两组的重复电诱发电位记录。研究结果：经过生理盐水中的条件化处理后，电极接触的阻抗降低了31%；然而，在电极阵列植入后，并未观察到临床上有意义的差异。根据我们的数据，条件化处理后测量可重复性增加的假设未能得到证实。在生理盐水中，我们观察到44%的电极接触被气泡覆盖，这些气泡在植入后大部分消失。然而，这些气泡限制了生理盐水中条件化处理的效果。最后，条件化对参考电极刺激的影响约为阻抗总降低量的16%。研究结论：我们的数据不支持在MED-EL耳蜗植入术中，术中条件化处理在临床上是必需的。此外，体内电诱发电位记录可以考虑作为一种条件化电极接触的方法。研究意义：我们证实了常见的临床实践无需改变。