Validation of the Arm Profile Score in assessing upper limb functional impairments in people with multiple sclerosis

Background. Although upper limb (UL) impairments are widespread in people with Multiple Sclerosis (pwMS), there is limited quantitative evidence concerning their specific features. The aim of this study is to validate a synthetic measure based on kinematic data to define the degree of deviation from a physiologic pattern during the "hand to mouth" (HTM) task. Methods: Twenty pwMS (mean age 51.2 SD 11.1) years, Expanded Disability Status Scale (EDSS) score in the range 2-6.5, underwent a kinematic analysis of the HTM task using a motion capture system. Spatio-temporal parameters and synthetic indexes (Arm Variable Score, AVS and Arm Profile Score, APS) were calculated and compared with those of age-matched healthy individuals. Kinematic data were correlated with the EDSS score and clinical tests such as the Nine Hole Peg Test (NHPT) and hand-grip strength (HGS). Findings: PwMS exhibit reduced velocity, increased movement duration, sway of adjusting and frequency of direction changes as well as higher APS values (15.4 degrees vs. 8.6 degrees, P < 0.001) with respect to controls due to alterations in trunk flexion-extension, shoulder abduction-adduction, flexion-extension and rotation and elbow flexion-extension. Moderate-to-large correlations were found between APS and EDSS (rho = 0.609, P < 0.001), NHPT (rho = 0.468, P = 0.03) and HGS (rho = -0.627 P < 0.001). Interpretation: The kinematic analysis of HTM provides useful information in quantifying UL impairments in pwMS. The APS index appears suitable to represent UL movement deviations from the physiological pattern in pwMS and to assess disease progression or effectiveness of pharmacologic and rehabilitative treatments effectiveness.