This will be a randomized, blinded, sham-controlled trial. The medical device used, Soterix Medical 1x1 tDCS stimulator, is capable of delivering either real or sham tDCS and has been used in many randomised controlled trials in stroke patients.

50 patients with subacute stroke and severe upper limb weakness within 8 weeks of stroke on transfer to TTSH stroke rehab wards will be recruited over a period of 10 months. Recruited patients will be randomized into the intervention and control arms in a 1:1 ratio.

The primary objective is to determine the clinical efficacy, technical feasibility and safety of anodal tDCS therapy to the unaffected hemisphere in hospitalized subacute stroke patients with severe arm weakness.

Inclusion Criteria:

• First ever unilateral ischaemic or haemorrhagic stroke, as documented by CT or MRI scans
• Age 21-80 years, both males and females
• Within 8 weeks of stroke onset
• Severe weakness of one upper limb, defined by a Shoulder Abduction and Finger Extension (SAFE) score < 5 (Medical Research Council grading)
• Provision of informed consent by patient or a legal guardian in accordance with the local ethics committee guidelines and the Declaration of Helsinki

Exclusion Criteria:

• Bilateral hemispheric or cerebellar strokes
• Pre-existing arm pathology (e.g. contracture, severe pain, etc.) on the affected side
• Presence of brain implants, and previous insertion of external ventricular drains.
• Metallic implants at the level of the neck, mouth cavity and below are permitted (e.g. Cardiac stents, dental implants, pacemakers and other metallic objects)
• A history of spontaneous seizures, epilepsy, brain tumour, and cranial surgery
• Severe cognitive impairment (MOCA Score <10) that would hinder sufficient understanding of the instructions
• Pregnancy

To protect the privacy of participants. Preparing IPD for sharing can also be time-consuming and resource-intensive.