Abstract 15: Surface Electrical Stimulation Does Not Improve Hand Function in Subacute Stroke

Abstract

Background and Objective: Prior studies have suggested that EMG-triggered and cyclic surface electrical stimulation (ES) mediated hand opening exercises facilitate motor recovery of the hemiparetic upper limb. EMG-triggered ES is believed to more effective than cyclic ES due to the addition of cognitive input to trigger the ES. However, these 2 types of ES have not been compared in a placebo controlled randomized clinical trial. This trial tested the hypothesis that EMG-triggered ES is more effective than cyclic ES in facilitating the motor recovery of the hemiparetic upper limb, and that both are more effective than placebo. Methods: Stroke survivors who were within 6-mo of their stroke were randomized to treatment with EMG-triggered ES (EMG), cyclic ES (cyclic) or placebo. The EMG group received the ES by initiating volition finger extension. The resulting EMG from the extensor digitorum communis (EDC) then triggered the ES. The cyclic group received the ES to the EDC in a repetitive timed sequence without volitional activation. For the placebo group, a stimulating electrode was placed on the dorsal forearm away from the motor point of the EDC, and the stimulation intensity was set at sensory threshold with no motor activation. Duty cycle was gradually increased from 5 sec on/20 sec off to 5 sec on/5 sec off as tolerated for all participants. All participants were treated 80 min/day, 5 days a week for 8 weeks. Motor impairment (Fugl-Meyer Motor Assessment-FMA) and activities limitation (Arm Motor Abilities Test-AMAT) outcomes were assessed in a blinded manner at baseline, mid-treatment, end of treatment and at 1, 3 and 6-mo after end of treatment. Data were analyzed using repeated measures ANOVA in an intent-to-treat manner. Results: A total of 122 participants enrolled in the study (EMG: 41; Cyclic: 39; and placebo: 42). Baseline characteristics were comparable between groups. All three groups experienced significant improvement in FMA (F=54.5, p<0.001) and AMAT (F=21.7, p<0.001) scores. However, there were no differences between treatment groups (FMA: F=0.25, p=0.78; AMAT: F=0.43, p=0.55). Conclusions: EMG-triggered and cyclic ES were no more effective than placebo in facilitating the motor recovery of the hemiparetic upper limb. The improvements in FMA and AMAT scores likely represent natural recovery. However, since sensory stimulation without motor activation may not be placebo, the possibility of therapeutic effect of sensory stimulation cannot be ruled out in the present design.