Abstract
BackgroundArm impairment in Multiple Sclerosis (MS) is commonly assessed with clinical scales, such as Action Research Arm Test (ARAT) which evaluates the ability to handle and transport smaller and larger objects. ARAT provides a complete upper limb assessment, as it considers both proximal arm and hand, but suffers from subjectivity and poor sensitivity to mild impairment. In this study an instrumented ARAT is proposed to overcome these limitations and supplement the assessment of arm function in MS.MethodsARAT was executed by 12 healthy volunteers and 21 MS subjects wearing a single inertial sensor on the wrist. Accelerometers and gyroscopes signals were used to calculate the duration of each task and its sub-phases (reaching, manipulation, transport, release and return). A jerk index was computed to quantify movement smoothness. For each parameter, z-scores were calculated to analyze the deviation from normative data. MS subjects were clinically assessed with ARAT score, Nine-Hole Peg test (9HPT) and Fahn Tremor Rating Scale (FTRS).ResultsARAT tasks executed by MS patients were significantly slower (duration increase: 70%) and less smooth (jerk increase: 16%) with respect to controls. These anomalies were mainly related to manipulation, transport and release sub-movements, with the former showing the greatest alterations. A statistically significant decrease in movement velocity and smoothness was also noticed in patients with normal ARAT score. Z-scores related to duration and jerk were strongly correlated with ARAT rating (r < -0.80, p < 0.001) and 9HPT (r < -0.75, p < 0.001) and were significantly different among MS sub-groups with different levels of arm impairments (p < 0.001). Moreover, Z-score related to manipulation-phase jerk was significantly correlated with the FTRS rating of intention tremor (r = 0.84, p < 0.001).ConclusionsThe present study showed that the proposed method is able to discriminate between control and MS groups and to reveal subtle arm alterations not detectable from ARAT score. Validity was shown by high correlations between instrumental variables and clinical ratings. These results suggested that instrumented ARAT could be a valid quick and easy-to-use method for a sensitive quantification of arm function in MS. Inclusion of finger-mounted sensors could complement present findings and provide further indications about hand function in MS.
Highlights
Arm impairment in Multiple Sclerosis (MS) is commonly assessed with clinical scales, such as Action Research Arm Test (ARAT) which evaluates the ability to handle and transport smaller and larger objects
All patients presented with reduced hand dexterity, as shown by 9HPT scores that were always higher than the threshold value typical of healthy adults with comparable age (19 s ± 2 s [40])
Results related to the cluster analysis performed on ARAT, 9HPT and Fahn Tremor Rating Scale (FTRS) ratings revealed the existence of three sub-groups of MS subjects with different level of upper limb impairment: mild (n = 12), moderate (n = 5) and severe (n = 4)
Summary
Arm impairment in Multiple Sclerosis (MS) is commonly assessed with clinical scales, such as Action Research Arm Test (ARAT) which evaluates the ability to handle and transport smaller and larger objects. From a statistical point of view ordinal scales are reliable [11] and sensitive for measuring gross changes in motor performance but have less sensitivity to smaller and more specific changes [17,18] They suffer from poor sensitivity to mild impairment because of a significant ceiling effect [10,19]. Timed tests are more objective than ordinal scales, as the final score is represented by the time to complete the task They are less influenced by ceiling effect but they do not provide a complete assessment of upper limb function, as they involve only partial movements of proximal arm, mainly focusing on hand movements (e.g. Jebsen-Taylor Test) and gross/fine manual dexterity (Box & Block and Nine Hole Peg Test). There is a need to develop new easy-to-use measurement tools which can provide more objective and detailed evaluation of upper limb function, necessary for the analysis of the specific deficit of each subject and for the definition of personalized rehabilitation treatments
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