OBJECTIVE We aim to non-invasively facilitate activation of spared neural circuits after cervical spinal cord injury (SCI) and amyotrophic lateral sclerosis (ALS). We developed and tested a novel configuration for cervical transcutaneous spinal stimulation (cTSS). METHODS cTSS was delivered via electrodes placed over the midline at ~T2-T4 levels posteriorly and ~C4-C5 levels anteriorly. Electromyographic responses were measured in arm and hand muscles across a range of stimulus intensities. Double-pulse experiments were performed to assess homosynaptic post-activation depression (PAD). Safety was closely monitored. RESULTS More than 170 cTSS sessions were conducted without major safety or tolerability issues. A cathode-posterior, 2 ms biphasic waveform provided optimal stimulation characteristics. Bilateral upper extremity muscle responses were easily obtained in subjects with SCI and ALS. Resting motor threshold at the abductor pollicis brevis muscle ranged from 5.5 to 51.0 mA. As stimulus intensity increased, response latencies to all muscles decreased. PAD was incomplete at lower stimulus intensities, and decreased at higher stimulus intensities. CONCLUSIONS Posteroanterior cTSS has the capability to target motor neurons both trans-synaptically via large-diameter afferents and non-synaptically via efferent motor axons. SIGNIFICANCE Posteroanterior cTSS is well tolerated and easily activates upper extremity muscles in individuals with SCI and ALS.

中文翻译：

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颈椎后前路经皮脊髓刺激靶向腹侧和背侧神经根

目标我们的目标是在颈脊髓损伤 (SCI) 和肌萎缩侧索硬化 (ALS) 后无创地促进备用神经回路的激活。我们开发并测试了一种用于颈椎经皮脊柱刺激 (cTSS) 的新型配置。方法 cTSS 是通过放置在中线上后~T2-T4 水平和前~C4-C5 水平的电极传送的。在一系列刺激强度下测量手臂和手部肌肉的肌电图反应。进行双脉冲实验以评估同突触激活后抑制 (PAD)。安全受到严密监控。结果 进行了 170 多次 cTSS 会议，没有出现重大安全性或耐受性问题。阴极-后 2 ms 双相波形提供了最佳的刺激特性。在患有 SCI 和 ALS 的受试者中很容易获得双侧上肢肌肉反应。拇短外展肌的静息运动阈值范围为 5.5 至 51.0 mA。随着刺激强度的增加，对所有肌肉的反应延迟都会减少。PAD 在较低刺激强度下不完整，在较高刺激强度下下降。结论 后前部 cTSS 有能力通过大直径传入和非突触通过传出运动轴突跨突触地靶向运动神经元。意义 在 SCI 和 ALS 患者中，后前位 cTSS 具有良好的耐受性并且很容易激活上肢肌肉。所有肌肉的反应潜伏期都减少了。PAD 在较低刺激强度下不完整，在较高刺激强度下下降。结论 后前部 cTSS 有能力通过大直径传入和非突触通过传出运动轴突跨突触地靶向运动神经元。意义 在 SCI 和 ALS 患者中，后前位 cTSS 具有良好的耐受性，并且很容易激活上肢肌肉。对所有肌肉的反应潜伏期都减少了。PAD 在较低刺激强度下不完整，在较高刺激强度下下降。结论 后前部 cTSS 有能力通过大直径传入和非突触通过传出运动轴突跨突触地靶向运动神经元。意义 在 SCI 和 ALS 患者中，后前位 cTSS 具有良好的耐受性并且很容易激活上肢肌肉。