Simultaneous Ashworth measurements and electromyographic recordings in tetraplegic patients

A recent prevalence study of 353 spinal cord injured (SCI) individuals in the greater Stockholm area showed problematic spasticity in 30% of this population. To treat spasticity, the evaluation becomes crucial. The modified Ashworth scale (MAS) is the clinically most-used scale to grade degree of spasticity. This study evaluated whether the MAS correlated with electromyographic (EMG) recordings of muscle activity.

This cross-sectional study was performed at an outpatient clinic that has the responsibility to do a standardized, yearly follow-up of all SCI patients in the greater Stockholm area. Thirty-eight SCI individuals met the inclusion criteria; 15 of the 38 were randomly selected for the study. They were all motor-complete tetraplegic men; mean age was 33 years and mean time since injury was 9 years. Spasticity evaluation was performed by flexing and extending the knees during simultaneous EMG recordings and MAS assessment of the thigh muscle activity.

Eighty percent of the individual EMG recordings correlated significantly with the corresponding Ashworth measurements. The spastic resistance, as measured both clinically and electromyographically, was stronger and lasted longer during extension than flexion movements. Spearman coefficients for correlation of quantitative spasticity measures with MAS grades were calculated. EMG and clinical measures of spasticity were more closely correlated for flexion movements. Among EMG parameters, duration of movement-associated electrical activity invariably correlated significantly with the MAS grades (p < .05). Furthermore, Ashworth measurements of movement-associated spasticity showed a positive correlation with the EMG parameters mean, peak, and start to peak of electrical activity. Each increasing grade on the MAS corresponded to increasing myoelectric activity levels for each movement.

EMG parameters were significantly positively correlated with simultaneous MAS measurements of the spastic muscle contraction. The Ashworth scale may therefore accurately reflect the movement-provoked spasticity in motor-complete tetraplegic patients.