Nickolls P, Collins D F, Gorman R B, Burke David, Gandevia S C
Spinal Injuries Research Center, Prince of Wales Medical Research Institute and University of New South Wales, Australia.
Brain. 2004 Mar;127(Pt 3):660-70. doi: 10.1093/brain/awh073. Epub 2004 Jan 28.
Percutaneous electrical stimulation over tibialis anterior and triceps surae was performed in 14 patients with traumatic spinal cord injury (SCI) to look for evidence that 'extra contractions' can develop, beyond those due to activation of the motor axons beneath the stimulating electrodes. Criteria for the extra contractions included marked asymmetry of force with respect to stimulation, progressively rising force during stimulation of constant amplitude and frequency, and force remaining high after stimulation frequency had returned to the control level following a high-frequency burst. Twelve of the 14 patients showed evidence of such behaviour, more frequently in triceps surae than tibialis anterior. Force or electromyographic activity commonly outlasted the stimulation in these patients. There was no apparent correlation between the completeness or level of injury and the ability to induce the behaviour. Evidence of force potentiation and 'habituation' was also seen. Eleven of the 14 patients exhibited hyper-reflexia and reported spontaneous spasms, but there was no obvious association with the extra contractions. It is concluded that non-classical behaviour of neurons within the spinal cord can contribute to the extra contractions evoked by electrical stimulation over muscles in spinal cord-injured subjects. This central contribution is less easy to obtain than in intact healthy subjects, all of whom showed the phenomenon. These contractions are consistent with the activation of plateau potentials in spinal neurons and, if so, plateau potentials may contribute to a patient's clinical manifestations.
对14例创伤性脊髓损伤（SCI）患者的胫前肌和小腿三头肌进行经皮电刺激，以寻找证据证明除了刺激电极下方运动轴突激活所引起的收缩外，还能产生“额外收缩”。额外收缩的标准包括刺激时力的明显不对称、在恒定幅度和频率刺激期间力逐渐增加，以及在高频爆发后刺激频率恢复到对照水平时力仍保持较高。14例患者中有12例表现出这种行为，小腿三头肌比胫前肌更常见。在这些患者中，力或肌电图活动通常在刺激后持续存在。损伤的完整性或水平与诱导这种行为的能力之间没有明显的相关性。还观察到了力增强和“习惯化”的证据。14例患者中有11例表现出反射亢进并报告有自发痉挛，但与额外收缩没有明显关联。得出的结论是，脊髓内神经元的非经典行为可导致脊髓损伤患者肌肉电刺激诱发的额外收缩。与所有表现出该现象的完整健康受试者相比，脊髓损伤患者获得这种中枢性贡献不太容易。这些收缩与脊髓神经元平台电位的激活一致，如果是这样，平台电位可能导致患者的临床表现。
