The Effect of The Five-Session Dual-tDCS On Lower-Limb Performance in Sub-Acute Stroke
Condition: Stroke, Ischemic
MeSH terms: Stroke; Ischemic Stroke
Study type: Interventional

Summary: 
      The aim of the present study is to determine the effect of the five-session dual-tDCS combine
      with physical therapy on gait performance, balance and lower limbs muscle strength in
      patients with subacute stroke.
    

Detailed description: 
      Stroke is a leading cause of long term disability. The recovery of motor function after
      stroke is often incomplete, despite classical rehabilitation techniques. In the beginning of
      the 21st century, transcranial direct current stimulation (tDCS) was introduced as a
      non-invasive tool to reversibly modulate brain excitability in humans in which a device sends
      constant low direct current (DC) delivered to the area of interest through the electrodes.
      Transcranial direct current stimulation (tDCS) has been used in neurorehabilitation to
      benefit ischemic stroke patients at different stage of stroke especially during acute,
      sub-acute and chronic phase with positive and safety reports.

      After stroke, the excitability of the lesioned hemisphere is decreased and seen like
      overactive of the excitability of non-lesioned hemisphere. Abnormally high interhemispheric
      inhibition (IHI) drive from intact to lesioned hemisphere has been reported. The neural
      plasticity begins in early stages after stroke. Prevent the imbalance IHI and increase the
      excitability of the lesioned hemisphere in the early phase would be a beneficial for stroke
      rehabilitation.

      Based on the polarity-specific effects, anodal tDCS increases cortical excitability and
      cathodal tDCS decreases cortical excitability. Transcranial direct current stimulation (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 lesioned hemisphere: anode over the lesioned hemisphere and the cathode as the
      reference electrode placed over the contra-orbital area ii) to down regulate excitability of
      the non-lesioned hemisphere and rebalance IHI: cathode over the non-lesioned 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. There are few evidences
      showing that tDCS (monocephalic and bi-hemispheric/dual-tDCS) could improve lower limb
      performance at immediate and at least 3 months. However, there is still unclear effect on
      gait performance and muscle strength.

      Recently, dual-hemisphere tDCS, in which, excites one hemisphere using anodal stimulation and
      inhibits the other by cathodal stimulation has been described in healthy volunteers to
      greater enhance hand motor learning compared to uni-hemispheric tDCS. The corresponding
      tDCS-induced changes were reported in imaging study to involve interhemispheric interactions.

      Dual-tDCS has been more recent used in rehabilitation aiming to reduce the inhibition exerted
      by the non-lesioned hemisphere on the lesioned hemisphere and restore the normal balance of
      the IHI. Dual-tDCS combined with training or simultaneous occupational/physical therapy has
      been reported to improve motor skill learning and functions of the paretic upper limb in
      chronic stroke patients.

      Lower-limb functions are commonly disabling after stoke, however, less studies have focused
      the effect of tDCS on lower limb functions. A single session of anodal tDCS over the lower
      limb M1 has reported to acutely enhance the effect of motor practice of the paretic ankle,
      force production of the paretic knee extensors, and postural stability in chronic stroke
      patients. A study showed an improvement of walking speed immediately after a single session
      of dual-tDCS alone in sub-acute stroke patients .

      Based on the previous study, 1-2 mA current intensity of tDCS is usually used for modulating
      brain activity. The proper current density delivered is between 0.029-0.008 mA/cm 2. The
      higher current density, the longer lasting, stronger, and deeper cortical neuron stimulation.
      Therefore, 2 mA current intensity of tDCS was applied in stroke patients for lower limb
      performance improvement. Following homologous brain regions, the motor area of lower
      extremities is in depth and previous studies demonstrated that current intensity 2 mA of tDCS
      could pass through the lower extremities area of the brain.

      Moreover, Tahtis et al, 2013 found that using 2 mA of dual-tDCS could improve walking speed
      immediately after a single session in sub-acute stroke and Klomjai et al, 2018 found that a
      single session of dual-tDCS 2 mA with physical therapy in sub-acute stroke immediately
      improved sit to stand performance greater than physical therapy alone. The mechanisms of
      actions was hypothesized that when stimulation continuously has effect on neuronal plasticity
      changes. Therefore, they suggested that further study shall implement more sessions of
      dual-tDCS combined with physical therapy to improve lower limb performance and determine the
      long lasting-after effect.

      The effect of 5-consecutive sessions dual-tDCS during physical therapy on upper limb
      performance showed significant improvement of upper limb motor functions and maintained at
      least 1 week. In this study, long-lasting effect was demonstrated at least one week to three
      months. There are evidences that 5 consecutive days of uni-hemisphere tDCS appeared to
      improve lower limb motor functions without serious adverse effects in patients with stroke.It
      is still unclear for the effect of multiple sessions of dual-tDCS on gait performance and
      muscle strength as well as the long lasting after-effect of multiple sessions of dual-tDCS.

      Therefore, the aim of the present study is to investigate the efficacy of 5 consecutive
      sessions of dual-tDCS combined with conventional physical therapy on the lower limb functions
      after stroke in sub-acute. Clinical outcomes for lower limb performance evaluations will
      consist of muscle strength assessed by hand-held dynamometer, the Time up and go test for
      lower limb functional performance, Five times sit to stand test for dynamic balance and
      muscle strength, and the Zebris Force distribution measurement (FDM) for gait analysis.
    

Intervention name(s): Transcranial direct current stimulation
Intervention type(s): Device
Intervention description(s): This instrument will be used to induce post-stroke motor recovery, two different monocephalic montages are typically used to restore excitability in the lesioned hemisphere and to down regulate excitability of the non-lesioned hemisphere and rebalance Interhemispheric inhibition. each participant will undergo a 20-minute period of tDCS, applied at 2 mA through a pair of saline-soaked surface sponge electrodes (35 cm2).
Allocation: Randomized
Intervention model: Factorial Assignment
Masking: Triple (Participant, Investigator, Outcomes Assessor)
Primary purpose: Treatment