Immediate Effects of transcranial Direct Current Stimulation (tDCS) on post-stroke shoulder pain.

Shoulder pain is a common post-stroke symptom, with a prevalence ranging from 30% to 65% among stroke survivors. It can significantly limit participation in rehabilitation, reduce the use of the affected upper limb, and impair performance in activities of daily living, thereby negatively affecting functional recovery.

Transcranial direct current stimulation (tDCS) is a non-invasive brain stimulation technique that delivers low-intensity electrical current through scalp electrodes to modulate cortical excitability. In recent years, tDCS has shown promising results in reducing post-stroke pain. The primary motor cortex (M1) is the most commonly targeted stimulation site, and research suggests that stimulation of this region may influence pain perception by modulating cortical networks involved in pain processing.

Previous research has explored the effects of repeated tDCS sessions on outcomes such as motor recovery and chronic pain following stroke. However, there is limited evidence regarding the immediate analgesic effects of a single session of tDCS on post-stroke shoulder pain. Understanding whether tDCS can produce an immediate reduction in pain may be clinically beneficial, as it could reduce discomfort and facilitate greater participation in upper limb rehabilitation.

Therefore, this study aims to assess whether tDCS has an immediate effect on reducing post-stroke shoulder pain when combined with usual care. A 2 mA direct current will be applied using tDCS with the anode placed over the ipsilesional primary motor cortex (M1) and the cathode over the contralesional primary motor cortex (cM1) for 20 minutes. Participants will be divided into two groups: an active tDCS group and a sham tDCS group. Both groups will receive conventional physiotherapy, which includes relevant precautions, sling prescription, and Transcutaneous Electrical Nerve Stimulation (TENS). TENS will be applied for 20 minutes at a frequency of 80 Hz with a pulse width of 200 µs.

Pain intensity will be assessed using the Visual Analog Scale (VAS) and the McGill Pain Questionnaire. Pain measurements will be recorded at baseline, immediately after the intervention, and 2 hours post-treatment to evaluate the immediate analgesic effect of tDCS.