Abstract：
Stroke is a leading cause of adult disability that results in motor deficits and reduced independence. Regaining independence relies on motor recovery, particularly regaining function of the hand and arm. This review presents evidence from human studies that have used transcranial magnetic stimulation (TMS) to identify neurophysiological mechanisms underlying upper limb motor recovery early after stroke. TMS studies undertaken at the subacute stage after stroke have identified several neurophysiological factors that can drive motor impairment, including membrane excitability, the recruitment of corticomotor neurons, and glutamatergic and GABAergic neurotransmission. However, the inherent variability and subsequent poor reliability of measures derived from motor evoked potentials (MEPs) limit the use of TMS for prognosis at the individual patient level. Currently, prediction tools that provide the most accurate information about upper limb motor outcomes for individual patients early after stroke combine clinical measures with a simple neurophysiological biomarker based on MEP presence or absence, i.e. MEP status. Here, we propose a new compositional framework to examine MEPs across several upper limb muscles within a threshold matrix. The matrix can provide a more comprehensive view of corticomotor function and recovery after stroke by quantifying the evolution of subthreshold and suprathreshold MEPs through compositional analyses. Our contention is that subthreshold responses might be the most sensitive to reduced output of corticomotor neurons, desynchronized firing of the remaining neurons, and myelination processes that occur early after stroke. Quantifying subthreshold responses might provide new insights into post-stroke neurophysiology and improve the accuracy of prediction of upper limb motor outcomes.
摘要：
中风是成人残疾的主要原因，导致运动障碍和独立性下降。恢复独立依赖于运动恢复，特别是恢复手和手臂的功能。这篇综述提供了来自人类研究的证据，这些研究使用经颅磁刺激（TMS）来确定中风后早期上肢运动恢复的神经生理机制。在中风后亚急性阶段进行的TMS研究已经确定了几种可导致运动障碍的神经生理因素。包括膜兴奋性，皮质醇神经元的募集，以及谷氨酸能和GABA能神经传递。然而,运动诱发电位(MEP)测量的固有变异性和随后的低可靠性限制了TMS在个体患者水平的预后中的应用.目前,为卒中后早期患者提供最准确的上肢运动结果信息的预测工具将临床测量与基于MEP存在或不存在的简单神经生理学生物标志物相结合,即MEP状态。这里,我们提出了一个新的组成框架，以检查阈值矩阵内多条上肢肌肉的MEP。通过成分分析量化亚阈值和超阈值MEP的演变，该矩阵可以提供中风后皮质运动功能和恢复的更全面视图。我们的论点是，亚阈值反应可能对皮质运动性神经元的输出减少最敏感，剩余神经元的非同步放电，和中风后早期发生的髓鞘形成过程。定量亚阈值反应可能为中风后神经生理学提供新的见解，并提高上肢运动结果预测的准确性。
