Cerebrovascular disease is a major cause of disability worldwide. The catastrophic burden of stroke is more dramatic in low- and middle- income countries, and the scarcity of evidence-based rehabilitation interventions represents a major challenge to global health care. Upper limb weakness is frequent after stroke, but there is no universally accepted treatment to effectively improve hand function in patients with moderate and severe motor impairment. These are the patients in deepest need of rehabilitative interventions. This project addresses this important issue, by testing effects of a novel approach. We will non-invasively stimulate the brain and peripheral nerves in order to enhance effects of motor training aided by an electrical stimulation device in patients with moderate to severe hand weakness. Our hypothesis is that brain stimulation, when added to peripheral nerve stimulation, will enhance effects of motor training to a greater extent than brain stimulation alone, peripheral stimulation alone, or no stimulation.

The goal of this study is to compare the effects of FES in close association with either transcranial direct current stimulation (tDCS) alone, peripheral nerve stimulation (PNS)alone, tDCS + PNS or sham tDCS + sham PNS, in patients with moderate to severe upper limb weakness, in a cross-over design. The working hypothesis of this proof-of-principle study is that either tDCS or PNS will enhance effects of functional electrical stimulation (FES) to a greater extent than placebo tDCS and PNS, and that the combination of tDCS and PNS will further improve motor outcomes than either tDCS or PNS alone.

The interventions will consist of outpatient motor training of the paretic wrist with FES in four experimental sessions separated by two weeks. In each session, either active tDCS + sham PNS, active PNS + sham tDCS,active tDCS + active PNS or sham tDCS + sham PNS will be applied. PNS will be applied for 2 hours and tDCS will be applied in the last 20 minutes before completion of PNS. The order of the sessions will be randomized across patients. Before the first session, patients will be familiarized with the FES device.

Inclusion Criteria:

• Age, 18 years or older;
• First-ever, ischemic or hemorrhagic stroke at least six months before, confirmed by computed tomography or magnetic resonance imaging;
• Moderate to severe motor impairment of an upper limb, defined as a score between 7 and 50 on the Fugl-Meyer Assessment of Sensorimotor Recovery after stroke, a scale with scores for upper limb ranging from 0 (no function) to 66 (normal function;
• Ability to provide written Informed Consent (patient or legal representative);
• Ability to comply with the schedule of interventions and evaluations in the protocol.

Exclusion Criteria:

• Lack of ability to voluntarily activate any active range of wrist extension;
• Anesthesia of the paretic hand;
• Stroke lesions affecting entirely the hand knob area of the motor cortex120;
• Stroke lesions affecting the cerebellum or the brain stem;
• Severe spasticity at the paretic elbow, wrist, or fingers, defined as a score of >3 on the Modified Ashworth Spasticity Scale;
• Active joint deformity;
• Uncontrolled medical problems such as end-stage cancer or renal disease;
• Pregnancy;
• Seizures;
• Pacemakers;
• Other neurological disorders such as Parkinson's disease;
• Psychiatric illness including severe depression;
• Aphasia or serious cognitive deficits that preclude comprehension of the experimental protocol or ability to provide consent. A score in the Minimental State Examination lower than 23/30 points will be used for patients with higher than 1 year of education, and a score lower than 19/30 will be used for patients with 1 year of education or less.

It was a cross-sectional study. Of twenty two participants who started the study, one participant only participated in one of the four sessions, while the remainder participated in all four. Of the 21 participants who completed four sessions, one was removed from analyses after meeting exclusion criteria