Stroke is the major cause of disability worldwide. A number of neurological functions are impaired by stroke; the most common impairment is motor disability contralateral to the stroke lesion side. Despite rehabilitation, the motor function outcome after stroke is often incomplete, and dexterity deficits are a considerable handicap to stroke survivors . Motor recovery after stroke is related to neural plasticity, which refers to the ability of the brain to develop new neuronal interconnections, acquire new functions, and compensate for impairment [2,3]. Therefore, various strategies based on neural plasticity are developing that aim to enhance motor recovery [4,5]. In particular, many reports have shown that non-invasive brain stimulation (NIBS) techniques help improve the efficacy of rehabilitative strategies employed after stroke by using physiological peculiarity that can alter the cortical excitability. The idea is that modulation of cortical excitability may induce neural plasticity and/or interfere with maladaptive neural activation, which subsequently weakens motor function and limits motor recovery . Repetitive transcranial magnetic stimulation (rTMS) and transcranial direct current stimulation (tDCS) are NIBS techniques that can alter excitability of the human cortex . rTMS is defined as repetition of TMS; high-frequency rTMS increases cortical excitability, whereas low-frequency rTMS suppresses cortical excitability . Theta burst stimulation (TBS) has also been reported as an effective rTMS method. It uses repeating bursts of very low-intensity combined-frequency rTMS . Each burst consists of 3 stimuli (delivered at 50 Hz) repeating at 5 Hz. TBS can be used in 2 ways: a continuous train is used to suppress cortical excitability and an intermittent pattern is used to enhance cortical excitability. tDCS is another commonly used NIBS technique. There are 2 types of tDCS: anodal tDCS increases the excitability of the stimulated cortex, whereas cathodal tDCS decreases the excitability of the stimulated cortex . NIBS therapy for motor stroke aims to augment neural plasticity and improve motor function based on the interhemispheric competition model. The interhemispheric competition model proposes that motor deficits in stroke patients are due to reduced output from the affected hemisphere and excessive interhemispheric inhibition from the unaffected hemisphere to the affected hemisphere [9,10]. Therefore, using NIBS, improvement in motor deficits can be achieved by increasing the excitability of the affected hemisphere or decreasing the excitability of the unaffected hemisphere [11,12]. No relevant adverse effects of NIBS, such as epileptic seizure induction, have been reported to occur in stroke patients when current safety guidelines regarding the intensity, frequency, and time of stimulation are adhered to [13,14].
Takeuchi, N. (2013). Overview of Non-Invasive Brain Stimulation for Motor Recovery After Stroke. International Journal of Physical Medicine & Rehabilitation, 01(02). https://doi.org/10.4172/2329-9096.1000114