Neuroscience Research Australia, Randwick, New South Wales, Australia.
School of Biomedical Sciences, University of New South Wales, New South Wales, Kensington, Australia.
Physiol Rep. 2023 Jun;11(11):e15692. doi: 10.14814/phy2.15692.
Transcutaneous spinal cord stimulation (TSS) is purported to improve motor function in people after spinal cord injury (SCI). However, several methodology aspects are yet to be explored. We investigated whether stimulation configuration affected the intensity needed to elicit spinally evoked motor responses (sEMR) in four lower limb muscles bilaterally. Also, since stimulation intensity for therapeutic TSS (i.e., trains of stimulation, typically delivered at 15-50 Hz) is sometimes based on the single-pulse threshold intensity, we compared these two stimulation types. In non-SCI participants (n = 9) and participants with a SCI (n = 9), three different electrode configurations (cathode-anode); L1-midline (below the umbilicus), T11-midline and L1-ASIS (anterior superior iliac spine; non-SCI only) were compared for the sEMR threshold intensity using single pulses or trains of stimulation which were recorded in the vastus medialis, medial hamstring, tibialis anterior, medial gastrocnemius muscles. In non-SCI participants, the L1-midline configuration showed lower sEMR thresholds compared to T11-midline (p = 0.002) and L1-ASIS (p < 0.001). There was no difference between T11-midline and L1-midline for participants with SCI (p = 0.245). Spinally evoked motor response thresholds were ~13% lower during trains of stimulation compared to single pulses in non-SCI participants (p < 0.001), but not in participants with SCI (p = 0.101). With trains of stimulation, threshold intensities were slightly lower and the incidence of sEMR was considerably lower. Overall, stimulation threshold intensities were generally lower with the L1-midline electrode configuration and is therefore preferred. While single-pulse threshold intensities may overestimate threshold intensities for therapeutic TSS, tolerance to trains of stimulation will be the limiting factor in most cases.
经皮脊髓电刺激(TSS)据称可改善脊髓损伤(SCI)后的运动功能。然而,还有几个方法学方面需要探讨。我们研究了刺激配置是否会影响双侧四个下肢肌肉的脊髓诱发电位运动反应(sEMR)所需的刺激强度。此外,由于治疗性 TSS 的刺激强度(即刺激的串,通常以 15-50Hz 传递)有时基于单脉冲阈值强度,因此我们比较了这两种刺激类型。在非 SCI 参与者(n=9)和 SCI 参与者(n=9)中,使用单脉冲或刺激串记录了三种不同的电极配置(阴极-阳极);L1-中线(脐下)、T11-中线和 L1-ASIS(髂前上棘;仅非 SCI),比较了在股直肌、内收肌、胫骨前肌、内腓肠肌中 sEMR 阈值强度。在非 SCI 参与者中,L1-中线配置的 sEMR 阈值低于 T11-中线(p=0.002)和 L1-ASIS(p<0.001)。对于 SCI 参与者,T11-中线和 L1-中线之间没有差异(p=0.245)。与非 SCI 参与者相比,刺激串期间的脊髓诱发电位运动反应阈值降低了约 13%(p<0.001),但在 SCI 参与者中没有差异(p=0.101)。用刺激串时,阈值强度略低,sEMR 的发生率也明显降低。总体而言,L1-中线电极配置的刺激阈值强度通常较低,因此更受青睐。虽然单脉冲阈值强度可能会高估治疗性 TSS 的阈值强度,但在大多数情况下,对刺激串的耐受性将是限制因素。