# A Meta-Analysis on Dual Protocols for Chronic Stroke Motor Recovery: Robotic Training and tDCS
###### Abstract  
Two popular chronic stroke rehabilitation protocols are robotic-assisted movements and transcranial direct current stimulation (tDCS). Separately, both protocols have produced encouraging motor recovery improvements. An intriguing question remains: what happens to motor recovery when both protocols are administered together? Do the two protocols together produce additive dual effects? This systematic review and meta-analysis investigated the dual effect of combining robotic training and tDCS. We investigated the potential effects of tDCS protocols in addition to robotic-training programs on motor recovery of the upper and lower extremities post-stroke. A systematic literature search identified 20 qualified studies that used robotic training combined with tDCS protocols for upper limb (i.e., 15 studies) and lower limb (i.e., 5 studies) post-stroke rehabilitation. Individuals in the subacute and chronic stages of recovery were investigated. The 20 included studies compared additive effects of the combined protocols with robotic training sham control groups. Further, we estimated short-term and long-term treatment effects of the combined protocols. The random-effects model meta-analyses failed to find any significant short-term and long-term motor improvements in the upper extremities after the combined treatments. However, robotic-assisted movements combined with tDCS protocols revealed significant moderate transient and sustained improvements in functions of the lower limbs post-stroke. These meta-analytic findings suggest clinical implications concerning coupled top-down and bottom-up training protocols (i.e., robotic training and tDCS combined), which will allow us to make progress toward post-stroke motor recovery. stroke; robotic; transcranial direct current stimulation; rehabilitation; meta-analysis +
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protocol: brain stimulation affecting the central nervous system; (b) a bottom-up protocol: functional electrical stimulation or specific movements influencing the peripheral nervous system; or (c) combining the two novel stroke treatment protocols [12; 13]. Two promising post-stroke treatment protocols are transcranial direct stimulation (tDCS) and robotic-assisted movements [14; 15]. Non-invasive brain stimulation protocols such as tDCS have become popular treatments for post-stroke motor rehabilitation [16; 17]. Many tDCS studies have focused on stimulating the primary motor cortex (M1), which is located in the dorsal region of the frontal lobe and is related to controlling the motor system [14; 16]. Attaching tDCS surface electrodes to the M1 region of the ipsilesional hemisphere and applying a weak electrical current (0.5-2 mA) to the area continuously for 10-30 min routinely induces changes in cortical excitability that may persist for nearly 60 min [18; 19]. Presumably, anodal stimulation increases cortical excitability whereas cathodal stimulation decreases excitability [20]. Frequently, when tDCS is provided before or during (i.e., offline or online) traditional stroke rehabilitation programs, motor actions are re-acquired more quickly in comparison to tDCS alone [21; 22]. This favorable evidence is reported with fixed and variable stimulation techniques as well as various stimulation intensities. Moreover, these positive effects on motor recovery were found in both the upper and lower extremities during two retention tests: immediate (1 week after treatment) and delayed (24 weeks after treatment). Thus, the potential short-term and long-term benefits of tDCS on individuals post-stroke may address each of the three common stroke stages (i.e., acute, subacute, and chronic) [14; 23]. Granted, some researchers argue that standardizing tDCS electrode placement, stimulation intensity, and treatment duration would be ideal for stroke patients and rehabilitation therapists [24; 25]. Regardless, diverse tDCS and stroke motor recovery studies continue to report beneficial effects.