Stroke is the second cause of death worldwide and the majority of the survivors remain with motor impairments. Inhibition of the motor cortex of the unaffected hemisphere has emerged as a potential intervention to enhance effects of other rehabilitation strategies on improvement of motor performance of the paretic upper limb. In this proof-of-concept study we will evaluate the effects of inhibition of the motor cortex of the unaffected hemisphere associated with robotic therapy on improvement of motor performance of the paretic upper limb in the early phase post-stroke.

The main goal of this study is to test the proof of concept of benefits of inhibition of the motor cortex of the unaffected hemisphere on learning evaluated by improvement in kinematics of motor performance, in patients with upper limb paresis in the early phase post-stroke. For this purpose, patients will be randomized to receive real or sham transcranial direct current stimulation before a session of robotic therapy. Data will be collected by kinematic assessment performed automatically by the robot at baseline, immediately after and 24h after the intervention.

The working hypothesis is that one session of upper limb motor training will lead to improvement of performance in metrics of kinematics, and this improvement will be maintained up to 24h after the end of the training.

Inclusion Criteria:

Ischemic or hemorrhagic stroke onset from 3 days to 9 weeks before, confirmed by computed tomography or magnetic resonance imaging.

Motor impairment of an upper limb, defined as a score between 1 - 3 in the Medical Research Council Scale, for at lest one the following movements: elbow extension, shoulder flexion, or shoulder extension.

Ability to provide written informed consent.

Ability to comply with the schedule of interventions and evaluations in the protocol.

Exclusion Criteria:

Severe spasticity at the paretic elbow, wrist or fingers, defined as a score of > 3 in the Modified Ashworth Spasticity Scale.

No active shoulder and elbow movements

Uncontrolled medical problems such as end-stage cancer or renal disease

Pregnancy

Potential contraindications to transcranial direct current stimulation: history of seizures, lesions on the scalp, intracranial metal implants, prior intracranial surgery, use of drugs that interfere on cortical excitability (such as antiepileptic drugs, benzodiazepines)

Other neurological disorders such as Parkinson's disease

Psychiatric illness

Aphasia or severe cognitive deficits that compromise comprehension of the experimental protocol or ability to provide consent.

Hemineglect

Cerebellar lesions or on cerebellar pathways

Contact precautions