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.

This clinical study will be conducted in a sham-controlled, triple-blinded randomized controlled design. The patients will be recruited - by convenience sampling - from the outpatient population of University Hospitals of Geneva. Neurologists and the Medical Investigator (MI) will be contacted to recruit potential patients and a consent letter will be sent to them. The patients will be screened to determine whether a potential participant is eligible to be enrolled in the study or not. Only the MI will conduct the screening procedures, which include reviewing medical record and in-person interview. All screening activities will take 15-30 min., and they will be performed in a private screening room. Enrollment will occur after verifying the eligibility and obtaining the signed written consent form. Patients will be enrolled in the study only if they met all the inclusion criteria.

After enrollment, all patients will be scheduled to receive 10 visits over four consecutive weeks. Each patient will be seen initially (1st visit and 2nd visit) for about 150 min. to conduct all baseline measurements (T0), which will include clinical examinations (90 min.) using different standardized tests for lower limb function (with spatiotemporal gait recording), and to conduct the EEG evaluation (60 min.). The follow-up sessions (3rd visit to 8th visit) will last for around 75 min. (30 min. for the preparation and placement of electrodes + 45 min. for physical therapy). All patients will be scheduled to receive 6 tDCS stimulations combined with physical therapy over 2 weeks (3 sessions/week). The 9th visit and 10th visit will last for about 150 min. to carry out the measurement tests (with spatiotemporal gait recording) and to conduct the EEG session (T1). The final visit (i.e., 11th visit) will be scheduled to be 4 weeks (90 min.) after the 10th visit to evaluate the long-term effects using the same clinical measurement tests (with spatiotemporal gait recording) (T2).

All the participants, physical therapists and assessors will be blinded to the type of stimulation applied. An experienced physical therapist will take all the baseline measurements (T0), post-stimulation measurements immediately after the intervention (T1), and long-term effects 4 weeks after the end of the stimulation period (T2). Another experienced physical therapist (i.e., not involved in clinical evaluations) will carry out all tDCS sessions and will conduct physical therapy. The tDCS stimulator will be pre-programmed by a researcher not involved in the study, and both this physical therapist and the patients were not aware of the applied treatment. The EEG assessment will be performed by a co-investigator not involved in another part of the study. Randomization will be generated with an allocation sequence based on randomly selected block sizes of 3, 6 and 9 and provided with a computer random-number generator by a researcher not involved in the study. Patients will be stratified for age and stroke laterality at randomization. Therefore, all the patients will be randomly assigned to one of three groups at a rate of 1:1:1:

Group A (n=12): receive anodal tDCS over the affected primary motor cortex

Group B (n=12): receive anodal HD-tDCS over the affected primary motor cortex

Group C (n=12): receive sham stimulation (alternatively sham anodal tDCS or sham anodal HD-tDCS).

This study protocol has been approved by the research ethics committee in Geneva.

Eligibility Criteria:
Inclusion Criteria:

1. age ≥ 18 years,
2. first haemorrhagic or ischemic stroke,
3. time since stroke ≥ 12 months,
4. unilateral lower limb hemiparesis with a Fugl-Meyer score (lower limb portion) less than 28 (out of a maximum score of 34),
5. walking deficit with a Functional Ambulation Categories (FAC) score of more than 3,
6. able to walk for 6 minutes with or without a walking aid, with or without a break, at a self-determined comfort pace,
7. ability to concentrate and follow the study protocol,
8. have given informed consent

Exclusion Criteria:

1. second stroke during the protocol,
2. botulinum toxin injection less than 3 months before the start of the protocol,
3. impaired alertness with a Montreal Cognitive Assessment (MoCA) score below 23,
4. metal object or implant near the stimulated area,
5. pacemaker,
6. vestibular disorders or vertigo,
7. severe dystonia or spasticity with a Modified Ashworth Scale score of 3 or more,
8. history of migraine,
9. severe osteoarticular comorbidities of the lower limb,
10. patients with one or more epileptic seizures,
11. severe language impairment,
12. 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,
13. Pregnant woman