Overall, there are two forms of non-invasive brain stimulation strategies strongly considered (but not yet FDA approved) for stroke recovery.
Non-invasive brain stimulation has been studied for treating Stroke, Traumatic brain injury and Parkinson’s disease. Non-invasive brain stimulation has been shown to be safe. It may be used to target the damaged area of the brain to help restore function or a stimulate a different part of the brain to compensate for lost function elsewhere. Symptoms targeted include weakness, chronic pain, depression, impaired thinking skills, swallowing and communication disorders, involuntary muscle movement and coordination disorders. Repetitive trans-cranial magnetic stimulation uses a magnetic field placed near patient's head. Trans-cranial direct current stimulation uses weak electrical currents applied directly on patient's head temporarily.
Klomjai et al reviewed in 2015 the studies on effects of magnetic and direct trans-cranial stimulation on stroke recovery and concluded that these modalities show promise for use in stroke rehabilitation (Ann Phys Rehabil Med. 2015 Sep;58(4):220-224).
As of 2018 Dionísio et al study concluded that though majority of studies on repetitive trans-cranial magnetic stimulation showed potential in improving motor function, some studies showed contradictory evidence and further studies are still needed to help standardize operating protocols and show conclusive evidence for efficacy of these interventions. (J Stroke Cerebrovasc Dis. 2018 Jan;27(1):1-31).
A 2019 systemic review of meta-analyses of randomized controlled studies for sub-acute stroke rehabilitation by García-Rudolph et al concluded that using trans-cranial direct current stimulation showed moderate improvement along with virtual reality (e.g. virtual reality gaming use for rehabilitation), constraint-induced movement (constraining the "good" limb to force use of the "weak" limb) and augmented exercises therapy (e.g. task-specific training with increased time spent or number of repetitions) techniques, whereas evidence for Eastern Medicine techniques including Moxibustion (form of heat therapy in which dried plant materials called "moxa" are burned on or very near the surface of the skin), Tai Chi, and acupuncture was too heterogeneous (Medicine (Baltimore) 2019 Feb;98(8):e14501).