Hemodynamic Response and Motor Functions Following Transcranial Direct Current Stimulation in Acute Stroke

It is generally accepted that transcranial direct current stimulation (tDCS) can induce change in cortical excitability and thus modulate brain plasticity in the human brain. tDCS has been used in neurorehabilitation to benefit ischemic stroke patients at different stages of stroke especially during acute, subacute, and chronic phase with positive and safety reports. After a unilateral stroke, the excitability of the affected hemisphere is decreased, an increase in the excitability of the unaffected hemisphere and an abnormally high interhemispheric inhibition (IHI) drive from the intact to lesioned hemisphere have been reported.

These neuronal reorganizations and plasticity begin in the very early stages after stroke. Prevent the abnormal IHI and thus increase the excitability of the affected hemisphere in the early phase would be beneficial for stroke rehabilitation.

Based on the polarity-specific effects, anodal tDCS increases cortical excitability and cathodal tDCS decreases cortical excitability. tDCS can be applied in two distinct montages: monocephalic and bi-hemispheric/dual-tDCS (applying two electrodes over both cerebral hemispheres at the same time). To induce post-stroke motor recovery, two different monocephalic montages are typically used: i) to restore excitability in the ipsilesional hemisphere: anode over the ipsilesional hemisphere and the cathode as the reference electrode placed over the contra-orbital area ii) to down-regulate excitability of the contralesional hemisphere and rebalance IHI: cathode over the contralesional hemisphere and the anode as the reference electrode. Dual-tDCS can be also applied, permitting simultaneous coupling of excitatory and inhibitory effects on both cortices. In the acute phase, there is few evidence regarding the effect of tDCS on upper or lower limbs motor functions. However no evidence for tDCS combined with training in the acute phase. Some previous studies reported a positive effect on upper or lower limbs performance of tDCS with physical therapy in subacute to chronic stroke. The immediate and long-term effectiveness of each tDCS montage (monocephalic and bi-hemispheric/dual-tDCS) without physical rehabilitation in acute stroke also has been reported. However, there is still unclear evidence regarding the best tDCS montage with conventional physical therapy for stroke recovery, especially for the early phase The mechanism underlying cortical excitability changes after tDCS is still elusive. However, one possible mechanism indicating a change in cortical activity is the subsequent variation in hemodynamic response. Since different montages of tDCS can induce different responses on brain excitability. Different methods have been developed for cerebral hemodynamic evaluations i.e. cerebral blood flow velocity (CBFV). Transcranial color-coded duplex ultrasonography (TCCD) has been used to measure CBFV through the major intracranial vessels through relatively thin bone windows. It is a non-invasive, relatively inexpensive, safe, and portable allowing bedside monitoring of CBFV that is convenient in the intensive care setting.

Five consecutive days for tDCS over the M1 appeared to be safe in acute stroke patient and tDCS over the M1 have been reported to improve motor functions and balance performance. Clinical outcomes that have been using in the clinical setting such as Fugl-Meyer Assessment for motor functions, strength assessed by hand-held dynamometer, Time up and go for dynamic balance and mobility, Five times sit to stand the test for dynamic balance and muscle strength will be used as a secondary motor outcome.

The aim of the present study is to investigate hemodynamic response and motor performance following difference montages of 5 tDCS sessions over the primary motor cortex (M1) applied before conventional physical therapy, at immediate after of 5-sessions and then follow up at 1 month.