IntroductionTranscutaneous spinal cord stimulation (TSCS), a non-invasive form of spinal cord stimulation, has been shown to improve motor function in individuals living with spinal cord injury (SCI). However, the effects of different types of TSCS currents including direct current (DC-TSCS), alternating current (AC-TSCS), and spinal paired stimulation on the excitability of neural pathways have not been systematically investigated. The objective of this systematic review was to determine the effects of TSCS on the excitability of neural pathways in adults with non-progressive SCI at any level.MethodsThe following databases were searched from their inception until June 2022: MEDLINE ALL, Embase, Web of Science, Cochrane Library, and clinical trials. A total of 4,431 abstracts were screened, and 23 articles were included.ResultsNineteen studies used TSCS at the thoracolumbar enlargement for lower limb rehabilitation (gait & balance) and four studies used cervical TSCS for upper limb rehabilitation. Sixteen studies measured spinal excitability by reporting different outcomes including Hoffmann reflex (H-reflex), flexion reflex excitability, spinal motor evoked potentials (SMEPs), cervicomedullay evoked potentials (CMEPs), and cutaneous-input-evoked muscle response. Seven studies measured corticospinal excitability using motor evoked potentials (MEPs) induced by transcranial magnetic stimulation (TMS), and one study measured somatosensory evoked potentials (SSEPs) following TSCS. Our findings indicated a decrease in the amplitude of H-reflex and long latency flexion reflex following AC-TSCS, alongside an increase in the amplitudes of SMEPs and CMEPs. Moreover, the application of the TSCS-TMS paired associative technique resulted in spinal reflex inhibition, manifested by reduced amplitudes in both the H-reflex and flexion reflex arc. In terms of corticospinal excitability, findings from 5 studies demonstrated an increase in the amplitude of MEPs linked to lower limb muscles following DC-TSCS, in addition to paired associative stimulation involving repetitive TMS on the brain and DC-TSCS on the spine. There was an observed improvement in the latency of SSEPs in a single study. Notably, the overall quality of evidence, assessed by the modified Downs and Black Quality assessment, was deemed poor.DiscussionThis review unveils the systematic evidence supporting the potential of TSCS in reshaping both spinal and supraspinal neuronal circuitries post-SCI. Yet, it underscores the critical necessity for more rigorous, high-quality investigations.

中文翻译：

---

脊髓损伤患者经皮脊髓刺激后神经通路兴奋性的调节：系统评价

简介经皮脊髓刺激 (TSCS) 是一种非侵入性脊髓刺激形式，已被证明可以改善脊髓损伤 (SCI) 患者的运动功能。然而，不同类型的 TSCS 电流，包括直流电 (DC-TSCS)、交流电 (AC-TSCS) 和脊髓配对刺激对神经通路兴奋性的影响尚未得到系统研究。本次系统评价的目的是确定 TSCS 对任何级别的非进行性 SCI 成人神经通路兴奋性的影响。方法从建立之初到 2022 年 6 月检索了以下数据库：MEDLINE ALL、Embase、Web of Science 、Cochrane 图书馆和临床试验。共筛选了4,431篇摘要，纳入23篇文章。结果19项研究使用TSCS在胸腰椎扩大术中进行下肢康复（步态和平衡），4项研究使用颈椎TSCS进行上肢康复。十六项研究通过报告不同的结果来测量脊髓兴奋性，包括霍夫曼反射（H-反射）、屈曲反射兴奋性、脊髓运动诱发电位（SMEP）、颈髓诱发电位（CMEP）和皮肤输入诱发肌肉反应。七项研究使用经颅磁刺激 (TMS) 诱导的运动诱发电位 (MEP) 测量皮质脊髓兴奋性，一项研究测量 TSCS 后的体感诱发电位 (SSEP)。我们的研究结果表明，AC-TSCS 后 H 反射和长潜伏期屈曲反射的幅度降低，同时 SMEP 和 CMEP 的幅度增加。此外，TSCS-TMS 配对联想技术的应用导致脊髓反射抑制，表现为 H 反射和屈曲反射弧的幅度减小。在皮质脊髓兴奋性方面，5 项研究的结果表明，除了涉及大脑重复 TMS 和脊柱 DC-TSCS 的配对联想刺激之外，DC-TSCS 后与下肢肌肉相关的 MEP 振幅增加。在一项研究中观察到 SSEP 潜伏期有所改善。值得注意的是，通过修改后的唐斯和布莱克质量评估评估的证据的整体质量被认为很差。讨论本综述揭示了支持 TSCS 在重塑 SCI 后脊髓和脊髓上神经元回路方面的潜力的系统证据。然而，它强调了进行更严格、高质量调查的迫切必要性。