Using surface electromyography to assess motor unit structural change post stroke

描述（由申请人提供）：肌肉无力是半球中风后限制运动功能的主要障碍之一。导致肌肉无力的机制之一是运动单元的结构改变，包括肌纤维直径减少、肌纤维损失，甚至麻痹性肌肉的运动轴突损失和运动神经元再神经支配。目前，我们对中风后运动单元结构改变程度的了解受到肌肉内记录技术的限制，这些技术既具有侵入性又效率低下。一种用于运动单元分析的新型表面肌电图（sEMG）记录和分解技术最近被开发出来并在神经完整的个体中进行了测试。该系统采用了一种独特的表面电极，非侵入性和高效率，可能同时产生大量的运动单元。因此，本建议的目的是：1)量化中风后麻痹肌运动单位大小减少的程度和频率。2)建立脑卒中幸存者轻瘫肌运动神经元再神经支配的稳健标志物。我们将记录32名中风幸存者在特定力水平的等长收缩时，麻痹性和对侧第一背骨间肌的肌电信号，我们也将记录32名神经功能完整、年龄匹配的对照受试者的肌电信号。我们将使用新的表面肌电信号分解算法提取单个运动单元的放电活动，并使用尖峰触发平均技术估计运动单元的形状特征。为了解决目标1，我们将计算关键的运动单元动作电位（MUAP）参数，包括峰值振幅、持续时间和均方根值，以估计运动单元大小。为了解决目标2，我们将量化MUAP的多相特性（即峰的数量）作为运动神经元再神经化的估计。我们还将研究运动单元的结构变化与运动损伤的严重程度之间的关系。我们假设，由于纤维大小减少和肌纤维损失，麻痹肌的运动单位大小减少，并且中风后麻痹肌中MUAP的多相变化（即峰数增加）也更明显。提出的研究将提供关于周围运动单元结构变化在肌肉无力中的作用的重要信息。本研究使用的新型非侵入性技术将提供一种有效的方法来系统地检查运动单元特征的变化，并有可能作为一种诊断工具来区分卒中中肌肉无力的中枢和外周起源。因此，所提出的工作可以为有针对性的康复治疗提供理论依据，有可能最大化中风幸存者的功能恢复。

DESCRIPTION (provided by applicant): Muscular weakness is one of the major impairments limiting motor function following a hemispheric stroke. One mechanism that can contribute to muscle weakness is the structural changes of the motor unit, including reduction of fiber diameter, muscle fiber loss, and even motor axon loss and motoneuron reinnervation of paretic muscles. Currently, our knowledge of the extent of such motor unit structural change post-stroke is limited by the constraints associated with intramuscular recording techniques, which are both invasive and inefficient. A novel surface electromyogram (sEMG) recording and decomposition technique for motor unit analysis has recently been developed and tested in neurologically intact individuals. The system utilizes a unique surface electrode that is non-invasive and efficient, potentially yielding a large number of motor units simultaneously. Accordingly, the aims of this proposal are 1) To quantify the degree and frequency of the reduction in motor unit size in paretic muscle post-stroke. 2) To establish robust markers of motoneuron reinnervation in paretic muscle of stroke survivors. We will record the sEMG signals of both paretic and contralateral first dorsal interosseous muscles of 32 stroke survivors during isometric contractions at specified force levels, and we will also record the sEMG of 32 neurologically intact age-matched control subjects. We will extract single motor unit discharge activities using the novel sEMG decomposition algorithm, and estimate motor unit shape characteristics using the spike triggered averaging techniques. To address Aim 1, we will calculate key motor unit action potential (MUAP) parameters, including peak-peak amplitude, duration, and root mean squared values, as estimates the motor unit size. To address Aim 2, we will quantify the polyphasic properties (i.e., the number of peaks) of the MUAP as an estimate of motoneuron reinnervation. We will also examine the association between the structural changes in motor units and the severity of motor impairment. We hypothesize that the motor unit size in the paretic muscle is reduced, because of fiber size reduction and muscle fiber loss, and that the polyphasic changes (i.e., a larger number of peaks) in the MUAP are also more visible in the paretic muscle following a stroke. The proposed research will provide important information regarding the role of peripheral motor unit structural changes in muscle weakness. The novel and non-invasive techniques used here will provide an efficient way to systematically examine changes in motor unit characteristics, and can potentially serve as a diagnostic tool to distinguish central vs. peripheral origins of muscle weakness in stroke. The proposed work can thus provide a rationale for differentially targeted rehabilitation therapies with a potential to maximize functional recovery of stroke survivors.