Time-course analysis of stretch reflexes in hemiparetic subjects using an on-line spasticity measurement system

Spasticity after a stroke is usually assessed in a score form by subjective ly determining the resistance of a joint to an externally imposed passive m ovement. This work presents a spasticity measurement system for on-line qua ntifying the stretch reflex of paretic limbs. Four different constant stret ch velocities in a ramp-and-hold mode are used to elicit the stretch reflex of the elbow joint in spastic subjects. The subjects are tested at supine position with the upper limb stretched towards the ground, in contrast with the horizontally stretched movement used in other studies. By subtracting the baseline torque, reflex torque measured at a selected low stretch Veloc ity of 5 deg/sec, the influence of gravity torque and inertial in vertical stretching mode can be minimized. The averaged speed-dependent reflex torqu e (ASRT), defined as the measured torque deviated from the baseline torque, is used for quantifying the spastic hypertonia. Four subjects having incur red cerebrovascular accident (CVA) are recruited for time-course study in w hich the measurements are taken at 72 hours: one week, one month, three mon ths, and six months after onset of stroke. During the development of spasti city, the changes of ASRT and Velocity sensitivity of ASRT of the involved and the intact elbow joints are discussed. (C) 2000 Elsevier Science Ltd. A ll rights reserved.