Abstract：
OBJECTIVE: Despite the widespread use and technical improvement of cochlear implant (CI) devices over past decades, further research into the bioelectric bases of CI stimulation is still needed. Various stimulation modes implemented by different CI manufacturers coexist, but their true clinical benefit remains unclear, probably due to the high inter-subject variability reported, which makes the prediction of CI outcomes and the optimal fitting of stimulation parameters challenging. A highly detailed full head model that includes a cochlea and an electrode array is developed in this study to emulate intracochlear voltages and extracochlear current pathways through the head in CI stimulation.
METHODS: Simulations based on the finite element method were conducted under monopolar, bipolar, tripolar, and partial tripolar modes, as well as for apical, medial, and basal electrodes. Variables simulated included: intracochlear voltages, electric field (EF) decay, electric potentials at the scalp and extracochlear currents through the head. To better understand CI side effects such as facial nerve stimulation, caused by spurious current leakage out from the cochlea, special emphasis is given to the analysis of the EF over the facial nerve.
RESULTS: The model reasonably predicts EF magnitudes and trends previously reported in CI users. New relevant extracochlear current pathways through the head and brain tissues have been identified. Simulated results also show differences in the magnitude and distribution of the EF through different segments of the facial nerve upon different stimulation modes and electrodes, dependent on nerve and bone tissue conductivities.
CONCLUSIONS: Full head models prove useful tools to model intra and extracochlear EFs in CI stimulation. Our findings could prove useful in the design of future experimental studies to contrast FNS mechanisms upon stimulation of different electrodes and CI modes. The full-head model developed is freely available for the CI community for further research and use.
METHODS: Simulations based on the finite element method were conducted under monopolar, bipolar, tripolar, and partial tripolar modes, as well as for apical, medial, and basal electrodes. Variables simulated included: intracochlear voltages, electric field (EF) decay, electric potentials at the scalp and extracochlear currents through the head. To better understand CI side effects such as facial nerve stimulation, caused by spurious current leakage out from the cochlea, special emphasis is given to the analysis of the EF over the facial nerve.
RESULTS: The model reasonably predicts EF magnitudes and trends previously reported in CI users. New relevant extracochlear current pathways through the head and brain tissues have been identified. Simulated results also show differences in the magnitude and distribution of the EF through different segments of the facial nerve upon different stimulation modes and electrodes, dependent on nerve and bone tissue conductivities.
CONCLUSIONS: Full head models prove useful tools to model intra and extracochlear EFs in CI stimulation. Our findings could prove useful in the design of future experimental studies to contrast FNS mechanisms upon stimulation of different electrodes and CI modes. The full-head model developed is freely available for the CI community for further research and use.
摘要：
目标：尽管人工耳蜗（CI）设备在过去几十年中得到了广泛使用和技术改进，仍需要进一步研究CI刺激的生物电基础。由不同CI制造商实施的各种刺激模式共存，但他们真正的临床益处仍不清楚，可能是由于所报告的高受试者间变异性，这使得CI结果的预测和刺激参数的最佳拟合具有挑战性。在这项研究中，开发了一个非常详细的完整的头部模型，其中包括耳蜗和电极阵列，以模拟耳蜗内电压和耳蜗外电流路径通过头部inCI刺激。
方法：基于有限元方法的模拟是在单极，双极,三极,和部分三极模式，以及根尖，中间,和基础电极。模拟的变量包括：耳蜗内电压，电场（EF）衰减，头皮上的电势和通过头部的耳蜗外电流。为了更好地理解CI副作用，如面神经刺激，由耳蜗的寄生电流泄漏引起的，特别强调面神经EF的分析。
结果：该模型合理地预测了以前在CI用户中报告的EF值和趋势。已经确定了通过头部和脑组织的新的相关耳蜗外电流通路。模拟结果还显示了在不同刺激模式和电极下，通过面神经的不同节段的EF的大小和分布的差异。依赖于神经和骨组织的电导率。
结论：全头模型证明了对CI刺激中的耳蜗内和耳蜗外EF进行建模的有用工具。我们的发现可以证明对未来实验研究的设计有用，以对比刺激不同电极和CI模式时的FNS机制。开发的全头模型可免费供CI社区进一步研究和使用。
方法：基于有限元方法的模拟是在单极，双极,三极,和部分三极模式，以及根尖，中间,和基础电极。模拟的变量包括：耳蜗内电压，电场（EF）衰减，头皮上的电势和通过头部的耳蜗外电流。为了更好地理解CI副作用，如面神经刺激，由耳蜗的寄生电流泄漏引起的，特别强调面神经EF的分析。
结果：该模型合理地预测了以前在CI用户中报告的EF值和趋势。已经确定了通过头部和脑组织的新的相关耳蜗外电流通路。模拟结果还显示了在不同刺激模式和电极下，通过面神经的不同节段的EF的大小和分布的差异。依赖于神经和骨组织的电导率。
结论：全头模型证明了对CI刺激中的耳蜗内和耳蜗外EF进行建模的有用工具。我们的发现可以证明对未来实验研究的设计有用，以对比刺激不同电极和CI模式时的FNS机制。开发的全头模型可免费供CI社区进一步研究和使用。
