Clustering index analysis of the surface electromyogram poststroke

The purpose of this study is to test the utility of a new and simple quantitative analysis method, termed clustering index (CI) method, using surface electromyogram (EMG) for evaluating spinal motoneuron involvement in muscle weakness of chronic stroke patients. Five stroke patients were recruited and instructed to generate isometric contraction for the first dorsal interosseous (FDI) muscle at difference force levels. The recording was performed in both paretic and contralateral sides of all stroke subjects, respectively. The Z-score, based on the CI method, was calculated on each side of a subject. Three subjects presented abnormally lower Z-scores on the paretic side, indicating dominant myopathic changes like muscle atrophy, while other 2 subjects presented relatively normal Z-scores. The normal observation in these 2 subjects may be induced by the combination of myopathic changes and neurogenic changes like degeneration of spinal motoneurons.