Vieira Taian M, Lemos Thiago, Oliveira Laura A S, Horsczaruk Carlos H R, Freitas Gabriel R, Tovar-Moll Fernanda, Rodrigues Erika C
Laboratorio di Ingegneria del Sistema Neuromuscolare (LISiN), Dipartimento di Elettronica e Telecomunicazioni, and PoliToBIOMed Lab, Politecnico di Torino, Turin, Italy.
Programa de Pós-Graduação em Ciências da Reabilitação, Centro Universitário Augusto Motta - UNISUAM, Rio de Janeiro, Brazil.
Front Neurol. 2019 Jun 26;10:686. doi: 10.3389/fneur.2019.00686. eCollection 2019.
Neuromuscular adaptations are well-reported in stroke survivors. The death of motor neurons and the reinnervation of residual muscle fibers by surviving motor neurons, for example, seem to explain the increased density of muscle units after stroke. It is, however, unknown whether reinnervation takes place locally or extensively within the muscle. Here we combine intramuscular and surface electromyograms (EMGs) to address this issue for medial gastrocnemius (MG); a key postural muscle. While seven stroke survivors stood upright, two intramuscular and 15 surface EMGs were recorded from the paretic and non-paretic gastrocnemius. Surface EMGs were triggered with the firing instants of motor units identified through the decomposition of both intramuscular and surface EMGs. The standard deviation of Gaussian curves fitting the root mean square amplitude distribution of surface potentials was considered to assess differences in the spatial distribution of motor unit action potentials and, thus, in the distribution of muscle units between limbs. The median number of motor units identified per subject in the paretic and non-paretic sides was, respectively, 2 (range: 1-3) and 3 (1-4). Action potentials in the paretic gastrocnemius were represented at a 33% wider skin region when compared to the non-paretic muscle (Mann-Whitney; = 0.014). Side differences in the representation of motor unit were not associated with differences in subcutaneous thickness (skipped-Spearman = -0.53; confidence interval for : -1.00 to 0.63). Current results suggest stroke may lead to the enlargement of the gastrocnemius muscle units recruited during standing. The enlargement of muscle units, as assessed from the skin surface, may constitute a new marker of neuromuscular plasticity following stroke.
神经肌肉适应性在中风幸存者中已有充分报道。例如，运动神经元的死亡以及存活的运动神经元对残余肌纤维的重新支配，似乎可以解释中风后肌肉单位密度的增加。然而，重新支配是在肌肉内局部发生还是广泛发生尚不清楚。在这里，我们结合肌内和表面肌电图（EMG）来解决腓肠肌内侧（MG）这个关键姿势肌的这一问题。在7名中风幸存者直立站立时，从患侧和非患侧腓肠肌记录了2个肌内和15个表面EMG。通过对肌内和表面EMG的分解确定运动单位的放电瞬间，以此触发表面EMG。通过拟合表面电位均方根振幅分布的高斯曲线的标准差来评估运动单位动作电位空间分布的差异，进而评估肢体间肌肉单位分布的差异。在患侧和非患侧，每位受试者识别出的运动单位中位数分别为2（范围：1 - 3）和3（1 - 4）。与非患侧肌肉相比，患侧腓肠肌的动作电位在皮肤区域的表现范围宽33%（曼 - 惠特尼检验； = 0.014）。运动单位表现的侧别差异与皮下厚度差异无关（斯皮尔曼偏相关系数 = -0.53； 的置信区间：-1.00至0.63）。目前的结果表明，中风可能导致站立时募集的腓肠肌肌肉单位增大。从皮肤表面评估的肌肉单位增大可能构成中风后神经肌肉可塑性的一个新标志。
