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

Lu Tang,Xiang Chen,Xu Zhang,Shuai Cao,De Wu,Gang Zhao

doi:10.3389/fnhum.2017.00130

Abstract

Muscle synergies are considered to be building blocks underlying motor behaviors. The goal of this study is 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 and 10 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. For each subject in TD group, four muscle synergies were extracted in each task. Whereas, fewer mature synergies were recruited in CP group, and many abnormal synergy structures specific to CP group appeared. In view 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 within task and the intra-subject similarity between tasks. Seven upper limb assessment (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 CP children. The experimental results demonstrated that these UPA metrics were able to assess upper limb motor function comprehensively and effectively. The proposed assessment method can serve as 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 CP clinical diagnosis and rehabilitation.

Highlights

Cerebral palsy (CP) describes a heterogeneous group of disorders affecting the development of movement and posture
Muscle synergy of the first subject (TD1) was selected as the template, and the muscle synergies from the remaining subjects were grouped based on the best-matching of W matrix
Take the muscle synergy extracted in Task 1 as example (Figure 4A), the first synergy mainly reflects the activity of latissimus dorsi (LAT) and TRAP; the second synergy reflects the activity of triceps brachii (TRI), DELA, DELM, and DELP; the third synergy consists of DELA and pectoralis major (PECM) whereas the fourth synergy consists of BRAD, BRAC, and BIC

Summary

Introduction

Cerebral palsy (CP) describes a heterogeneous group of disorders affecting the development of movement and posture. Apart from measuring the whole body motor function, the assessment of body partial motor function was developing gradually Some assessment methods, such as the Melbourne Assessment of Unilateral Upper Limb Function (Johnson et al, 1994), the Shriners Hospital for Children Upper Extremity Evaluation (SHUEE; Davids et al, 2006), and Fugl-Meyer Assessment (FMA; Fugl-Meyer et al, 1975) scale were frequently used in the clinic for the upper limb function assessment of CP patients (Krebs et al, 2009). As CP patients often suffered from abnormal muscle function such as muscle weakness and myotonia, which resulted in the abnormal pattern of surface electromyographic (sEMG) signal, researchers made some achievements in assessing CP motion abnormalities taking use of such phenomenon. The mean frequency of sEMG has a potential capability to evaluate the functional muscle strength during gait in CP children (Van Gestel et al, 2012)

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