Immediate and Late Modulation of Interhemipheric Imbalance With Bilateral Transcranial Direct Current Stimulation in Acute Stroke

Background Significant changes in neurophysiological and clinical outcomes in chronic stroke had been reported after tDCS; but there is a paucity of data in acute stroke. Objective We aimed to evaluate whether a tDCS-induced modulation of primary motor cortex excitability in patients with acute stroke enhances motor recovery associated with rehabilitation and induces differential neuroplasticity. Methods We conducted two experiments in acute stroke patients. In experiment 1 (14 patients), we tested the immediate effects of bilateral tDCS alone as compared to sham tDCS on recovery. Experiment 2 (20 patients) was designed to assess effects of bilateral tDCS delivered together with constraint-induced movement therapy (CIMT). In this experiment, we included a longer follow-up (3 months) and measured, in addition to the same clinical outcomes of experiment 1, changes of motor cortex excitability and the amount of promoted LTP-like activity. Results Despite the expected improvement at 1 week, none of the clinical measures showed any different modulation in dependence of CIMT and tDCS. On the neurophysiological assessments, on the other hand, the Real_tDCS group, compared to Sham_tDCS group, showed a reduction of inter-hemispheric imbalance when considering the differences of motor evoked potential between both 3-month and 1 week follow up (P = 0.007) and three month and baseline (P = 0.015). Conclusions Despite the lack of additional clinical changes, real bilateral tDCS, together with CIMT, significantly reduces inter-hemispheric imbalance between affected and unaffected hemispheres. These findings may shed light on plasticity changes in acute stroke and its potential impact in chronic phases.