Transcranial Direct Current Stimulation to Primary Motor Area Improves Hand Dexterity and Selective Attention in Chronic Stroke

Objective The aim of this study was to determine whether transcranial direct current stimulation (tDCS) applied to the primary motor hand area modulates hand dexterity and selective attention after stroke. Design This study was a double-blind, placebo-controlled, randomized crossover trial involving subjects with chronic stroke. Ten stroke survivors with some pinch strength in the paretic hand received three different tDCS interventions assigned in random order in separate sessionsanodal tDCS targeting the primary motor area of the lesioned hemisphere (M1(lesioned)), cathodal tDCS applied to the contralateral hemisphere (M1(nonlesioned)), and sham tDCSeach for 20 mins. The primary outcome measures were Purdue pegboard test scores for hand dexterity and response time in the color-word Stroop test for selective attention. Pinch strength of the paretic hand was the secondary outcome. Results Cathodal tDCS to M1(nonlesioned) significantly improved affected hand dexterity (by 1.1 points on the Purdue pegboard unimanual test, P = 0.014) and selective attention (0.6 secs faster response time on the level 3 Stroop interference test for response inhibition, P = 0.017), but not pinch strength. The outcomes were not improved with anodal tDCS to M1(lesioned) or sham tDCS. Conclusions Twenty minutes of cathodal tDCS to M1(nonlesioned) can promote both paretic hand dexterity and selective attention in people with chronic stroke.