École de Réadaptation, Faculté de Médecine, Université de Montréal, Pavillon du Parc, C.P.6128 Succ. Centre-ville, Montreal, Qc, H3C 3J7, Canada.
Centre for Interdisciplinary Research in Rehabilitation of Greater Montréal (CRIR), Montreal, Canada.
Exp Brain Res. 2021 Jun;239(6):1779-1794. doi: 10.1007/s00221-021-06081-0. Epub 2021 Mar 31.
Individuals with incomplete spinal cord injury (iSCI) show altered postural reactions leading to increased risk of falls. To investigate neural correlates underlying this deficit, we assessed the modulation pattern of the Soleus H-reflex in iSCI individuals following unexpected perturbations of a base of support. Ten men with iSCI (AIS D) and 8 age-matched controls (CTRL) stood on a force-platform randomly tilted forward or backward. The center of pressure (CoP) excursion, 95% confidence ellipse area and electromyographic (EMG) activity of the Soleus (SOL) and Tibialis Anterior (TA) muscles were analyzed. SOL H-reflex amplitude was assessed by stimulating the tibial nerve prior to and at 100, 150 and 200 ms following perturbation onset. Although SOL and TA short-latency EMG responses were comparable in both groups, long-latency EMG responses occurred later in the iSCI group for both directions: during backward tilt, a decrease in H-reflex amplitude was observed at all stimulus timings post-tilt in CTRL, but only at 200 ms in iSCI. The decrease in H-reflex amplitude was smaller in iSCI participants. During forward tilt, an increase in H-reflex amplitude was observed at 150 and 200 ms in the CTRL group, but no increase was observed in the iSCI group. Decreased and delayed SOL H-reflex amplitude modulation in the iSCI group accompanied impaired balance control as assessed clinically with the Berg Balance Scale and biomechanically through CoP displacement. Overall, delayed and reduced spinal reflex processing may contribute to impaired balance control in people with iSCI.
脊髓损伤不完全（iSCI）的个体表现出姿势反射改变，导致跌倒风险增加。为了研究这种缺陷的神经相关性，我们评估了 iSCI 个体在支撑基础突然变化后，比目鱼肌 H 反射的调制模式。10 名脊髓损伤不完全（AIS D）男性和 8 名年龄匹配的对照组（CTRL）人员站在力平台上，平台随机向前或向后倾斜。分析了中心压力（CoP）偏移、95%置信椭圆面积和比目鱼肌（SOL）和胫骨前肌（TA）的肌电图（EMG）活动。在刺激前和刺激后 100、150 和 200 毫秒评估比目鱼肌 H 反射幅度。尽管 SOL 和 TA 短潜伏期 EMG 反应在两组中相似，但 iSCI 组的长潜伏期 EMG 反应在两个方向上都较晚出现：向后倾斜时，在 CTRL 中，在倾斜后的所有刺激时间点都观察到 H 反射幅度减小，但在 iSCI 中仅在 200 毫秒时观察到。iSCI 参与者的 H 反射幅度减小幅度较小。向前倾斜时，在 CTRL 组中在 150 和 200 毫秒观察到 H 反射幅度增加，但在 iSCI 组中没有观察到增加。比目鱼肌 H 反射幅度调制的降低和延迟与 Berg 平衡量表评估的平衡控制受损以及 CoP 位移评估的生物力学平衡控制受损有关。总的来说，延迟和减少的脊髓反射处理可能导致脊髓损伤不完全的个体平衡控制受损。
