Transcranial Direct Current Stimulation for Gait Recovery Following Stroke

Background: Stroke is a leading cause of adult disability. The ability to walk is considered as the most important physical activity in daily life and strongly associated with quality of life in patients with stroke sequela. Conventional transcranial Direct Current Stimulation (tDCS) can induce mixed effects to improve gait impairment after stroke. The problem of limited focal specificity of tDCS may lead to an ineffective stimulation and in turn may be reduced the potential application of tDCS in clinical routine. High-definition transcranial Direct Current Stimulation (HD-tDCS) allows inducing, in a non-invasive way, a transient excitatory neuromodulation of a given cerebral region and to obtain a very focused cortical effect. However, the clinical and neurophysiological effects of HD-tDCS remain largely unknown for enhancing gait recovery in patients with stroke. The investigators hypothesize that anodal HD-tDCS will enhance neural interactions between motor networks and, thereby, improve motor processing and gait relearning. The investigators propose to carry out a study on chronic stroke patients involving anodal HD-tDCS of the affected primary motor cortex combined with a physical therapy.This study has three main objectives:To compare the effects of two techniques of tDCS (anodal tDCS, anodal HD-tDCS) on clinical recovery in patients with chronic stroke.To assess the effects of these brain stimulation techniques on brain reorganization with electroencephalography (EEG).To assess the effects of these brain stimulation techniques on spatiotemporal gait parameters during walking with wearable motion sensors.Methods: 36 patients with ischemic or hemorrhagic stroke will be randomly assigned to one of 3 groups: anodal tDCS, anodal HD-tDCS, or sham stimulation. Each group will receive the corresponding stimulation therapy 3 times per week for 2 weeks, simultaneously with physical therapy. Before (T0) and immediately after the treatment period (T1) and again one month later (T2), standardized assessments of sensorimotor function areas are obtained together with spatio-temporal analysis. Brain reorganization is assessed with EEG before and immediately after the treatment period. These recordings will be used to compare and investigate the clinical and physiological effects of each treatment modality.

Inclusion Criteria:age ≥ 18 years,first haemorrhagic or ischemic stroke,time since stroke ≥ 12 months,unilateral lower limb hemiparesis with a Fugl-Meyer score (lower limb portion) less than 28 (out of a maximum score of 34),walking deficit with a Functional Ambulation Categories (FAC) score of more than 3,able to walk for 6 minutes with or without a walking aid, with or without a break, at a self-determined comfort pace,ability to concentrate and follow the study protocol,have given informed consentExclusion Criteria:second stroke during the protocol,botulinum toxin injection less than 3 months before the start of the protocol,impaired alertness with a Montreal Cognitive Assessment (MoCA) score below 23,metal object or implant near the stimulated area,pacemaker,vestibular disorders or vertigo,severe dystonia or spasticity with a Modified Ashworth Scale score of 3 or more,history of migraine,severe osteoarticular comorbidities of the lower limb,patients with one or more epileptic seizures,severe language impairment,other neurological or psychiatric disorder with severe impact on motor skills and activities of daily living, such as neurodegenerative disease, Parkinson's disease and others,Pregnant woman