Spasticity measurement based on tonic stretch reflex threshold in stroke using a portable device

Abstract

Objectives: We investigated intra- and inter-evaluator reliability to quantify spasticity based on the tonic stretch reflex threshold (TSRT) and the correlation between TSRT and resistance to stretch.

Methods: Spasticity was evaluated in 20 subjects with chronic stroke-related spasticity using a portable device and the Modified Ashworth Scale (MAS). Evaluations were done on 2 days, by three evaluators. Biceps brachii EMG signals and elbow displacement were recorded during 20 elbow stretches applied at different velocities for each evaluation. Velocity-dependent dynamic stretch reflex thresholds (angle where EMG signal increased in the biceps for a given velocity of stretch) were recorded. These values were used to compute TSRT (excitability of motoneurons at 0 degrees /s). Spasticity was also measured with MAS.

Results: Reliability was moderately good for subjects with moderate to high spasticity (intra-evaluator: 0.46-0.68, and inter-evaluator: 0.53-0.68). The TSRT measure of spasticity did not correlate with resistance to stretch (MAS).

Conclusions: TSRT may be a more representative measure for subjects with moderate to high spasticity. Further improvements are suggested for the portable device in order to quantify all the levels of spasticity.

Significance: TSRT may be an alternative clinical measure to current clinical scales.