Quantitative measures of spasticity in post-stroke patients

Objective: Quantitative evaluation of muscle tone in post-stroke patients; correlation of biomechanical indices with conventional clinical scales and neurophysiological measures; characterization of passive and neural compone nts of muscle tone. Methods: Mechanical stretches of the wrist flexor muscles of 53 post-stroke patients were imposed by means of a torque motor at constant speed. Patien ts were clinically studied using the Ashworth scale for spasticity and the Medical Research Council score for residual muscle strength. The neurophysi ological measures were Hoffmann reflex latency, Hmax/Mmax ratio, stretch re flex threshold speed (SRTS), stretch reflex (SR) latency and area, passive (ISI) and total (TSI) stiffness indices. Results: Hmax/Mmax ratio, SR area, ISI and TSI values were significantly hi gher in patients, while SRTS was significantly lower. TSI, SRTS and SR area were highly correlated to the Ashworth score. Conclusions: This EMG-biomechanical technique allows an objective evaluatio n of changes in muscle tone in post-stroke patients, providing easily measu rable, quantitative indices of muscle stiffness. The linear distribution of these measures is particularly indicated for monitoring changes induced by treatment. The apparatus seems suitable to characterize neural stiffness, while difficulties were found in isolating the passive components, because of the occurrence of tonic EMG activity in most spastic patients. (C) 2000 Elsevier Science Ireland Ltd. All rights reserved.