Evaluation of Spastic Muscle in Stroke Survivors Using Magnetic Resonance Imaging and Resistance to Passive Motion

Abstract 

Ploutz-Snyder LL, Clark BC, Logan L, Turk M. 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≤.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≥.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≥.05). Both muscle groups showed an increase in T2 after exercise (≈30%, P≤.05); however, the affected sides did not show an increase (P≥.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.

Key Words: Atrophy, muscle, Magnetic resonance imaging, functional, Reflex, Rehabilitation, Torque