Department of Brain Repair and Rehabilitation, UCL Institute of Neurology, Queen Square, London WC1N 3BG, UK.
Eur J Neurosci. 2011 Dec;34(11):1839-46. doi: 10.1111/j.1460-9568.2011.07895.x. Epub 2011 Nov 14.
Functional imaging studies, using blood oxygen level-dependent signals, have demonstrated cortical reorganization of forearm muscle maps towards the denervated leg area following spinal cord injury (SCI). The extent of cortical reorganization was predicted by spinal atrophy. We therefore expected to see a similar shift in the motor output of corticospinal projections of the forearm towards more denervated lower body parts in volunteers with cervical injury. Therefore, we used magnetic resonance imaging-navigated transcranial magnetic stimulation (TMS) to non-invasively measure changes in cortical map reorganization of a forearm muscle in the primary motor cortex (M1) following human SCI. We recruited volunteers with chronic cervical injuries resulting in bilateral upper and lower motor impairment and severe cervical atrophy and healthy control participants. All participants underwent a T1-weighted anatomical scan prior to the TMS experiment. The motor thresholds of the extensor digitorum communis muscle (EDC) were defined, and its cortical muscle representation was mapped. The centre of gravity (CoG), the cortical silent period (CSP) and active motor thresholds (AMTs) were measured. Regression analysis was used to investigate relationships between trauma-related anatomical changes and TMS parameters. SCI participants had increased AMTs (P = 0.01) and increased CSP duration (P = 0.01). The CoG of the EDC motor-evoked potential map was located more posteriorly towards the anatomical hand representation of M1 in SCI participants than in controls (P = 0.03). Crucially, cord atrophy was negatively associated with AMT and CSP duration (r(2) ≥ 0.26, P < 0.05). In conclusion, greater spinal cord atrophy predicts changes at the cortical level that lead to reduced excitability and increased inhibition. Therefore, cortical forearm motor representations may reorganize towards the intrinsic hand motor representation to maximize output to muscles of the impaired forearm following SCI.
功能影像学研究使用血氧水平依赖信号，证明了脊髓损伤（SCI）后，前臂肌肉图向去神经支配的腿部区域的皮质重组。皮质重组的程度可以通过脊髓萎缩来预测。因此，我们预计在颈椎损伤的志愿者中，前臂皮质脊髓投射的运动输出会朝着更受神经支配的下半身部位发生类似的转变。因此，我们使用磁共振成像导航经颅磁刺激（TMS）技术，非侵入性地测量了慢性颈椎损伤导致双侧上下运动障碍和严重颈椎萎缩的 SCI 患者，初级运动皮层（M1）中前臂肌肉皮质图重组的变化。我们招募了慢性颈椎损伤导致双侧上下运动障碍和严重颈椎萎缩的志愿者和健康对照组参与者。所有参与者在 TMS 实验前都进行了 T1 加权解剖扫描。确定了伸指肌（EDC）的运动阈值，并对其皮质肌肉代表区进行了映射。测量了重心（CoG）、皮质静默期（CSP）和主动运动阈值（AMTs）。回归分析用于研究创伤相关解剖变化与 TMS 参数之间的关系。SCI 参与者的 AMTs 升高（P = 0.01），CSP 持续时间延长（P = 0.01）。与对照组相比，SCI 参与者 EDC 运动诱发电位图的 CoG 更向后位于 M1 的解剖手部代表区（P = 0.03）。至关重要的是，脊髓萎缩与 AMT 和 CSP 持续时间呈负相关（r²≥0.26，P<0.05）。总之，脊髓萎缩越大，预示着皮质水平发生变化，导致兴奋性降低和抑制性增加。因此，皮质前臂运动代表区可能会向内在手部运动代表区重新组织，以最大限度地提高 SCI 后受损前臂肌肉的输出。
