The Significance of Stretch Reflex Threshold Speed in Quantitative Assessment of Spasticity

ABSTRACT

OBJECTIVE: This study was designed to evaluate the usefulness of stretch reflex threshold speed (SRTS) in biomechanical assesment of spasticity of hemiplegic patients. METHOD: Thirty-eight hemiplegic patients and twenty-seven control subjects were studied. The spasticity of ankle plantar flexor muscles were assessed both clinically and biomechanically. Modified Ashworth scale (MAS) and Brunnstrom stage were used in clinical assessment. For biomechanical assessment, ankle plantar flexor muscles were stretched isokinetically while EMG signals were recorded simultaneously. SRTS was defined as a minimum angular velocity in which EMG signals evoked by stretch reflex were recorded. RESULTS: SRTSs of ankle plantar flexors were 128.1 47.1o/sec in control group, 163.7 79.7o/sec in intact legs, and 83.4 69.1o/sec in involved legs of hemiplegic group. STRS was significantly lower in involved legs of hemiplegic group than in intact legs of hemiplegic group and control group. Significant reverse correlation was observed between SRTS and MAS. There was significant difference in SRTS between MAS 0 group and other groups. The patients with Brunnstrom stage 3 and 4 groups showed decreased SRTS compared to the patients with other groups. CONCLUSION: SRTS is thought to reflect increased excitability of stretch reflex and seems to be one of useful parameters in quantitative assessment of spasticity.