Targeted tDCS Reduces the Expression of the Upper Limb Flexion Synergy in Chronic Hemiparetic Stroke

Research Objectives The emergence of abnormal movement synergies following a stroke presents a major limitation to the recovery of independent function(1). This study aims to explore a novel neuromodulatory technology based on a targeted tDCS(2-3) for reducing the upper limb flexion synergy post stroke. Design Randomized controlled trial. Setting Academic medical center. Participants Five adults (ages: 48-64 yrs. old) who suffered from a chronic hemiparetic stroke (Upper Extremity Fugl-Meyer score: 23-34) participated in this preliminary study. Interventions We collected electrical brain activity (EEG) and behavioral measures during a movement task before and after the TMS/EEG guided tDCS. The participants were seated on a Biodex rehabilitation chair and performed a shoulder abduction task at 30% of maximum effort with their paretic arm while they were receiving tactile electrical finger stimulation. TMS/EEG guided tDCS was applied using five small stimulation electrodes. Three participants received the anodal stimulation of tDCS that targeted the ipsilesional motor cortex and underlying corticospinal tracts, and two others received the cathodal stimulation inhibiting the contralesional somatosensory cortex. The anodal stimulation location was determined by TMS over the ipsilesional motor cortex(5). The cathodal stimulation location was determined by the somatosensory evoked potential over the contralesional somatosensory cortex(4). Main Outcome Measures We measured the shoulder abduction induced synergic elbow flexion torque as the main outcome measure to determine its expression. Results All tested participants showed a reduced expression of synergic elbow flexion after the targeted tDCS. Conclusions Our preliminary results suggested that facilitating the ipsilesional corticospinal tracts and inhibiting the contralesional sensory area in the brain, using the proposed tDCS technology, may help reducing motor impairments in chronic hemiparetic stroke. Author(s) Disclosures None