A Novel Interpretation of Sample Entropy in Surface Electromyographic Examination of Complex Neuromuscular Alternations in Subacute and Chronic Stroke

• Published in: IEEE transactions on neural systems and rehabilitation engineering Vol. 26; no. 9; pp. 1878 - 1888
• Main Authors: Tang, Xiao, Zhang, Xu, Gao, Xiaoping, Chen, Xiang, Zhou, Ping
• Format: Journal Article
• Language: English
• Published: United States IEEE 01.09.2018; The Institute of Electrical and Electronics Engineers, Inc. (IEEE)
• Subjects: Abnormalities; Acute Disease; Aged; Aged, 80 and over; Algorithms; Alternations; biomarker; Biomarkers; Brain; Chronic Disease; Cluster Analysis; Clustering; Diagnostic systems; Elbow; Electromyography; Electromyography - methods; Entropy; Female; Force; Functional Laterality; Humans; Isometric; Isometric Contraction; Male; Middle Aged; Motors; Muscle contraction; Muscle, Skeletal - physiopathology; Muscles; Neuromuscular; Neuromuscular changes; Neuromuscular Diseases - physiopathology; Paresis - physiopathology; Rehabilitation; sample entropy; Stroke; Stroke - physiopathology; Stroke Rehabilitation; surface electromyography; Surface morphology
• DOI: 10.1109/TNSRE.2018.2864317
• ISSN: 1534-4320; 1558-0210

The objective of this paper was to develop sample entropy (SampEn) as a novel surface electromyogram (EMG) biomarker to quantitatively examine post-stroke neuromuscular alternations. The SampEn method was performed on surface EMG interference patterns recorded from biceps brachii muscles of nine healthy control subjects, fourteen subjects with subacute stroke, and eleven subjects with chronic stroke, respectively. Measurements were collected during isometric contractions of elbow flexion at different constant force levels. By producing diagnostic decisions for individual muscles, two categories of abnormalities in some paretic muscles were discriminated in terms of abnormally increased and decreased SampEn. The efficiency of the SampEn was demonstrated by its comparable performance with a previously reported clustering index (CI) method. Mixed SampEn (or CI) patterns were observed in paretic muscles of subjects with stroke indicating complex neuromuscular changes at work as a result of a hemispheric brain lesion. Although both categories of SampEn (or CI) abnormalities were observed in both subacute and chronic stages of stroke, the underlying processes contributing to the SampEn abnormalities might vary a lot in stroke stage. The SampEn abnormalities were also found in contralateral muscles of subjects with chronic stroke indicating the necessity of applying interventions to contralateral muscles during stroke rehabilitation. Our work not only presents a novel method for quantitative examination of neuromuscular changes, but also explains the neuropathological mechanisms of motor impairments and offers guidelines for a better design of effective rehabilitation protocols toward improved motor recovery.