Department of Bioengineering, University of Pittsburgh, Pittsburgh, PA 15213, United States of America. Rehabilitation Neural Engineering Laboratories, 3520 Fifth Avenue, Suite 300, Pittsburgh, PA 15213, United States of America. Center for Neural Basis of Cognition, Pittsburgh, PA 15213, United States of America.
J Neural Eng. 2019 Dec 13;17(1):016011. doi: 10.1088/1741-2552/ab4a24.
We have shown previously that microstimulation of the lumbar dorsal root ganglia (L5-L7 DRG) using penetrating microelectrodes, selectively recruits distal branches of the sciatic and femoral nerves in an acute preparation. However, a variety of challenges limit the clinical translatability of DRG microstimulation via penetrating electrodes. For clinical translation of a DRG somatosensory neural interface, electrodes placed on the epineural surface of the DRG may be a viable path forward. The goal of this study was to evaluate the recruitment properties of epineural electrodes and compare their performance with that of penetrating electrodes. Here, we compare the number of selectively recruited distal nerve branches and the threshold stimulus intensities between penetrating and epineural electrode arrays.
Antidromically propagating action potentials were recorded from multiple distal branches of the femoral and sciatic nerves in response to epineural stimulation on 11 ganglia in four cats to quantify the selectivity of DRG stimulation. Compound action potentials (CAPs) were recorded using nerve cuff electrodes implanted around up to nine distal branches of the femoral and sciatic nerve trunks. We also tested stimulation selectivity with penetrating microelectrode arrays implanted into ten ganglia in four cats. A binary search was carried out to identify the minimum stimulus intensity that evoked a response at any of the distal cuffs, as well as whether the threshold response selectively occurred in only a single distal nerve branch.
Stimulation evoked activity in just a single peripheral nerve through 67% of epineural electrodes (35/52) and through 79% of the penetrating microelectrodes (240/308). The recruitment threshold (median = 9.67 nC/phase) and dynamic range of epineural stimulation (median = 1.01 nC/phase) were significantly higher than penetrating stimulation (0.90 nC/phase and 0.36 nC/phase, respectively). However, the pattern of peripheral nerves recruited for each DRG were similar for stimulation through epineural and penetrating electrodes.
Despite higher recruitment thresholds, epineural stimulation provides comparable selectivity and superior dynamic range to penetrating electrodes. These results suggest that it may be possible to achieve a highly selective neural interface with the DRG without penetrating the epineurium.
我们之前已经证明，在急性准备中，使用穿透微电极对腰椎背根神经节（L5-L7DRG）进行微刺激，可以选择性地募集坐骨神经和股神经的远端分支。然而，各种挑战限制了穿透电极的 DRG 微刺激的临床转化。对于 DRG 感觉神经界面的临床转化，放置在 DRG 神经外膜表面上的电极可能是一个可行的前进方向。本研究的目的是评估神经外膜电极的募集特性，并将其性能与穿透电极进行比较。在这里，我们比较了穿透和神经外膜电极阵列选择性募集的远端神经分支数量和刺激阈值强度。
在四只猫的 11 个神经节中，通过记录来自股神经和坐骨神经多个远端分支的逆行传播动作电位，来量化 DRG 刺激的选择性。使用神经套电极记录复合动作电位（CAP），这些电极被植入股神经和坐骨神经干的多达九个远端分支周围。我们还使用植入四只猫的十个神经节的穿透微电极阵列测试了刺激的选择性。进行了二进制搜索，以确定在任何远端套环处诱发反应的最小刺激强度，以及阈值反应是否仅选择性地发生在单个远端神经分支中。
通过 67%（52/87）的神经外膜电极和 79%（308/400）的穿透微电极，刺激仅在单个周围神经中引发活动。神经外膜刺激的募集阈值（中位数=9.67nC/相）和动态范围（中位数=1.01nC/相）明显高于穿透刺激（分别为 0.90nC/相和 0.36nC/相）。然而，对于通过神经外膜和穿透电极的刺激，募集的每个 DRG 的周围神经模式相似。
尽管募集阈值较高，但神经外膜刺激提供了与穿透电极相当的选择性和更高的动态范围。这些结果表明，有可能在不穿透神经外膜的情况下，使用 DRG 实现高度选择性的神经界面。
