Assessment of Upper Limb Motor Dysfunction for Children with Cerebral Palsy Based on Muscle Synergy Analysis

Muscle synergies are considered to be building blocks underlying motor behaviors. The goal of this studyi s to explore an objective and effective method to assess the upper limb motor dysfunction of cerebral palsy(CP)children from the aspect of muscle synergy analysis.Fourteen CP children and10 typically developed (TD) children were recruited to perform three similar upper limb motion tasks related to the movements of elbow and shoulder joints,and surface electromyographic (sEMG) signals were recorded from 10 upper arm and shoulder muscles involved in the defined tasks. Non-negative matrix factorization algorithm was used to extract muscle synergies and the corresponding activation patterns during three similar tasks.Foreachsubjectin TD group,fourmuscle synergies were extracted in each task.Whereas,fewer mature synergies were recruited in CP group,and many abnormal synergy structures specific toCP group appeared.Inview of neuromuscular control strategy differences,three synergy-related parameters were proposed and synergy structure similarity coefficient was found to have high ability in depicting the inter-subject similarity with in task and theintra-subjectsimilaritybetweentasks.Sevenupperlimbassessment(UPA)metrics, which were defined as the combinations of synergy structure similarity coefficients of three tasks,were proposed to assess the upper limb motor function of CPchildren.The experimental results demonstrated that these UPA metrics were able to assess upper limb motor function comprehensively and effectively.The proposed assessment method canserveas a promising approach to quantify the abnormality of muscle synergies,thus offering potential to derive a physiologically based quantitative index for assessing upper limb motor function in CPclinical diagnosis and rehabilitation