Dewald J P, Pope P S, Given J D, Buchanan T S, Rymer W Z
Sensory-Motor Performance Program, Rehabilitation Institute of Chicago, IL 60611, USA.
Brain. 1995 Apr;118 ( Pt 2):495-510. doi: 10.1093/brain/118.2.495.
To study abnormal spatial patterns of muscle activation in hemiparetic stroke, we compared EMG activity in paretic and contralateral elbow and shoulder muscles of 10 hemiparetic subjects during 1.5-s voluntary isometric contractions, against five to eight different loads. Isometric forces were generated in eight directions, referenced to a plane orthogonal to the long axis of the forearm, and were recorded by a three degrees of freedom load cell, mounted at the wrist. Surface and intramuscular EMGs of six elbow and six shoulder muscles were recorded from both impaired and contralateral upper extremities of each subject. The spatial characteristics of EMG activation of individual muscles were summarized using two measures. The first, called the 'net resultant EMG vector' is a new measure which calculated the vector sum of EMG magnitudes for each of the eight directions, and the second, index of EMG focus, is a measure of the range of EMG activation recorded for each load level. Use of these measures permitted us to describe spatial EMG characteristics quantitatively, which has not been done previously. We observed consistent and statistically significant shifts in the resultant EMG vector directions in the impaired limb, especially in shoulder and other proximal muscles. Significant increases in the angular range of EMG activity were also identified and were most evident at the elbow. Correlation analysis techniques were used to assess the degree of coactivation of different muscle pairs. There were consistent EMG coactivation patterns observed across all subjects (both normal and hemiparetic). However, in spasticparetic limbs, additional novel coactivational relationships were also recorded, especially between elbow flexors/shoulder abductors and elbow extensors/shoulder adductors. These novel coactivation patterns represent a reduction in the number of possible muscle combinations, or in the number of possible 'synergies' in the paretic limb of the stroke subject. This reduction in number of 'synergies' could result from a loss of descending command options; from an increased reliance on residual, descending brainstem pathways (such as the reticulospinal and vestibulospinal projections); from changes in spinal interneuronal excitability; or from a combination of several of these factors. The relative merits of these hypotheses are addressed.
为研究偏瘫性中风患者肌肉激活的异常空间模式，我们比较了10名偏瘫患者在1.5秒自主等长收缩期间，患侧与对侧肘部和肩部肌肉的肌电图（EMG）活动，对抗五到八种不同负荷。等长力在八个方向上产生，以垂直于前臂长轴的平面为参考，并由安装在手腕处的三自由度测力传感器记录。从每个受试者的患侧和对侧上肢记录了六块肘部肌肉和六块肩部肌肉的表面肌电图和肌内肌电图。使用两种测量方法总结了个体肌肉肌电图激活的空间特征。第一种称为“净合成肌电图向量”，是一种新的测量方法，计算八个方向上每个方向的肌电图幅度的向量和；第二种是肌电图聚焦指数，是对每个负荷水平记录的肌电图激活范围的一种测量。使用这些测量方法使我们能够定量描述肌电图的空间特征，这在以前尚未做到。我们观察到患侧肢体中合成肌电图向量方向存在一致且具有统计学意义的偏移，尤其是在肩部和其他近端肌肉中。还发现肌电图活动的角度范围有显著增加，且在肘部最为明显。使用相关分析技术评估不同肌肉对的共同激活程度。在所有受试者（正常和偏瘫）中均观察到一致的肌电图共同激活模式。然而，在痉挛性偏瘫肢体中，还记录到了额外的新型共同激活关系，尤其是在肘部屈肌/肩部外展肌与肘部伸肌/肩部内收肌之间。这些新型共同激活模式代表中风患者患侧肢体中可能的肌肉组合数量或可能的“协同作用”数量减少。这种“协同作用”数量的减少可能是由于下行指令选项的丧失；对残留的下行脑干通路（如网状脊髓和前庭脊髓投射）的依赖增加；脊髓中间神经元兴奋性的变化；或这些因素中的几种组合。本文探讨了这些假设的相对优点。
