Inria, University of Montpellier, CNRS, France.
J Neural Eng. 2018 Aug;15(4):046018. doi: 10.1088/1741-2552/aabeb9. Epub 2018 Apr 17.
Multipolar cuff electrode can selectively stimulate areas of peripheral nerves and therefore enable to control independent functions. However, the branching and fascicularization are known for a limited set of nerves and the specific organization remains subject-dependent. This paper presents general modeling and optimization methods in the context of multipolar stimulation using a cuff electrode without a priori knowledge of the nerve structure. Vagus nerve stimulation experiments based on the optimization results were then investigated.
The model consisted of two independent components: a lead field matrix representing the transfer function from the applied current to the extracellular voltage present on the nodes of Ranvier along each axon, and a linear activation model. The optimization process consisted in finding the best current repartition (ratios) to reach activation of a targeted area depending on three criteria: selectivity, efficiency and robustness.
The results showed that state-of-the-art configurations (tripolar transverse, tripolar longitudinal) were part of the optimized solutions but new ones could emerge depending on the trade-off between the three criteria and the targeted area. Besides, the choice of appropriate current ratios was more important than the choice of the stimulation amplitude for a stimulation without a priori knowledge of the nerve structure. We successfully assessed the solutions in vivo to selectively induce a decrease in cardiac rhythm through vagus nerve stimulation while limiting side effects. Compared to the standard whole ring configuration, a selective solution found by simulation provided on average 2.6 less adverse effects.
The preliminary results showed the rightness of the simulation, using a generic nerve geometry. It suggested that this approach will have broader applications that would benefit from multicontact cuff electrodes to elicit selective responses. In the context of the vagus nerve stimulation for heart failure therapy, we show that the simulation results were confirmed and improved the therapy while decreasing the side effects.
多极袖套电极可以选择性地刺激周围神经区域，从而实现独立功能的控制。然而，已知的神经分支和纤维束化仅限于有限的神经，并且特定的组织仍然取决于个体。本文提出了在没有神经结构先验知识的情况下使用袖套电极进行多极刺激的一般建模和优化方法。然后，根据优化结果进行了迷走神经刺激实验。
该模型由两个独立的组件组成：一个导联场矩阵，代表从施加的电流到每个轴突的郎飞节上的细胞外电压的传递函数；以及一个线性激活模型。优化过程包括根据三个标准（选择性、效率和鲁棒性）找到最佳的电流分配（比例），以达到靶向区域的激活。
结果表明，最先进的配置（三极横向、三极纵向）是优化解决方案的一部分，但也可能出现新的配置，这取决于三个标准和靶向区域之间的权衡。此外，对于没有神经结构先验知识的刺激，适当的电流比例的选择比刺激幅度的选择更为重要。我们成功地在体内评估了这些解决方案，通过迷走神经刺激选择性地诱导心率降低，同时限制副作用。与标准的整环配置相比，模拟找到的选择性解决方案平均减少了 2.6 种不良反应。
初步结果表明，使用通用神经几何形状进行模拟是正确的。这表明，这种方法将有更广泛的应用，将受益于多接触袖套电极来产生选择性反应。在心力衰竭治疗中迷走神经刺激的背景下，我们表明模拟结果得到了证实，并改善了治疗效果，同时减少了副作用。
