Evaluation of spastic muscle in stroke survivors using magnetic resonance imaging and resistance to passive motion

OBJECTIVE: To assess the feasibility of using magnetic resonance imaging (MRI) and resistance to passive movement to evaluate spastic muscle. DESIGN: T2-weighted MRI scans of the upper arm were obtained at rest and after the performance of upper-arm exercise. In addition, resistance to passive movement was measured subjectively (Modified Ashworth Scale [MAS]) and objectively by an isokinetic device while the arm was moved at varying speeds (stretch reflex torque). SETTING: Research laboratory. PARTICIPANTS: Six hemiplegic stroke survivors (single group) with spasticity in the elbow flexors and extensors. INTERVENTIONS: Not applicable. MAIN OUTCOME MEASURES: Strength, stretch reflex torque, MAS, MRI-derived muscle cross-sectional area (CSA), and transverse relaxation time (T2). RESULTS: The affected sides exhibited spasticity (as assessed through MAS), with the extensors displaying a range of 0 to 3, and the flexors between 1 and 1+. The affected muscle groups were significantly weaker than the unaffected muscle groups (extensors: 61% less, flexors: 65% less; P or =.05). The affected CSA of the triceps was 25% smaller than that of the unaffected side (P=.01), but the biceps muscle group was similar (5% less on the affected side, P> or =.05). There was a tendency (P=.07; effect size, .48) for the resting T2 to be higher in affected versus unaffected biceps, but triceps values were similar (P> or =.05). Both muscle groups showed an increase in T2 after exercise ( approximately 30%, P or =.05); however, the affected sides did not show an increase (P> or =.05). For both muscle groups, the affected side had a greater stretch reflex torque, with the range of torque values being greater than the range of MAS scores. CONCLUSIONS: MRI and quantitative resistance to passive movement may be useful in the evaluation of spasticity. This is clinically relevant for the development and evaluation of antispasticity treatments.