Does anodal trans-cranial direct current stimulation of the damaged primary motor cortex affects wrist flexor muscle spasticity and also activity of the wrist flexor and extensor muscles in patients with stroke? a Randomized Clinical Trial

Spasticity is a common symptom in stroke survivors. This study is double-blinded, sham-controlled randomized, clinical trial with three parallel arms. The aim of the study was to investigate the effects of anodal trans-cranial direct current stimulation (a-tDCS) over the damaged primary motor cortex (M1) on spasticity of the wrist flexor and also the activity of wrist flexor and extensor muscles in sub-acute stroke patients. This study was performed on 32 stroke patients. The patients are assigned to three groups (intervention, sham, and control). All participants in the first two groups received 20-min concurrent M1 a-tDCS or sham tDCS and functional electrical stimulation (FES) for 10 sessions (5 sessions per week), while participants in control group were given only 20-min FES for 10 sessions. Modified Ashworth scale of wrist flexors and also electromyography (EMG) activity of flexor carpi radialis (FCR) and extensor carpi radialis (ECR) were recorded before, immediately, and 1 month after the interventions. A significant reduction was shown in the MAS and EMG activity of FCR muscle at passive rest position of the wrist, immediately and 1 month after the intervention in M1 a-tDCS compared to sham and control groups (p < 0.001). Also, the EMG activity of FCR and ECR muscles during active wrist flexion and extension increased immediately and 1 month after intervention in M1 a-tDCS compared to the other groups, respectively (p < 0.001). M1 a-tDCS can significantly decrease the spasticity of wrist flexor muscle and also increase the wrist flexor and extensor muscles activity in stroke patients during active flexion and extension.