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tDCS in stroke rehabilitation

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Trans-cranial Direct Current Stimulation (tDCS) has been found effective and easy way in Stroke Rehabilitation. This is a literature review of few articles that reported the results of clinical trials of such DC stimulation in patients with stroke during their rehabilitation.

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tDCS in stroke rehabilitation

  1. 1. Transcranial Direct Current Stimulation (tDCS) in Stroke Rehabilitation By Md. Kafiul Islam Jan 26, 2013 A Literature Review
  2. 2. Introduction • What is tDCS – Non-invasive, painless brain stimulation – Constant, low-intensity DC by 2 electrodes • Types of Stimulation – Anodal : Excites neural activity – Cathodal : Inhibits neural activity • Advantages – Cheap, non-invasive, painless and safe – Easy to administer and equipment is portable – Least side effect (slight itching or tingling on scalp) Valuable tool for treatment of stroke recovery and other neuropsychiatric conditions • Depression, anxiety, Parkinson’s disease, and chronic pain • Cognitive improvement
  3. 3. Introduction (Cont…) • Stroke – Rapid loss of brain function due to disturbance in the blood supply to the brain – Brain cells (Neurons) suddenly die because of a lack of oxygen • After Effect – Inter-hemisphere Imbalance – Inability to move one or more limbs on one side of body – Inability to understand or formulate speech – Inability to see one side of the visual field
  4. 4. Paper-1 Review Transcranial direct current stimulation: a noninvasive tool to facilitate stroke recovery Arch Neurol. 2008 December
  5. 5. Review: Paper-1 UEFM: Measure of neurological and motor function.
  6. 6. Paper-2 Review Noninvasive Brain Stimulation in Stroke Rehabilitation NeuroRx. 2006
  7. 7. Review: Paper-2 Review at the effects of TMS and tDCS on motor cortical function and motor performance in healthy volunteers and in patients with stroke. Findings:  Both techniques have been proved to either enhance or suppress cortical excitability  Studies of cortical plasticity after stroke suggest that the damaged cortex has the potential for extensive reorganization
  8. 8. Paper-3 Review Transcranial Direct Current Stimulation of the Unaffected Hemisphere in Stroke Patients Neuroreport. 2005
  9. 9. Review: Paper-3 Recovery of function after a stroke is determined by a balance of activity in the neural network involving both the affected and the unaffected brain hemispheres. Increased activity in the affected hemisphere can promote recovery, while excessive activity in the unaffected hemisphere may represent a maladaptive strategy • Findings – both cathodal stimulation of the unaffected hemisphere and anodal stimulation of the affected hemisphere (but not sham transcranial direct current stimulation) improved motor performance significantly. Motor performance change (%) compared with baseline after stimulation of the primary motor cortex of the unaffected hemisphere (cathodal stimulation), stimulation of the primary motor cortex of the affected hemisphere (anodal stimulation)
  10. 10. Paper-4 Review Clinical research with transcranial direct current stimulation (tDCS): Challenges and future directions Neuroreport. 2005
  11. 11. Paper-4 Review TDCS dosage (1) Current dosage (measured in amperes); (2) Duration of stimulation; and (3) Electrode montage (size and position of all electrodes). Parameters of Stimulation TDCS parameters can vary widely and several factors need to be defined. These factors include electrode size and positioning, intensity, duration of stimulation, number of sessions per day, and interval between sessions. By varying these parameters, different amounts of electric current can be delivered, thus inducing diverse physiologic effects.
  12. 12. Paper-5 Review Excitability Changes Induced in the Human Motor Cortex by Weak Transcranial Direct Current Stimulation J. Physiol. 2000
  13. 13. Review: Paper-5 Cortical excitability change during current flow Polarity-specific after-effect of DC stimulation Findings  Excitation could be achieved selectively by anodal stimulation and inhibition by cathodal stimulation  By varying the current intensity and duration, the strength and duration of the aftereffects could be controlled The authors demonstrated in the intact human the possibility of a noninvasive modulation of motor cortex excitability by the application of weak direct current through the scalp
  14. 14. Electrode Shape & Salinity (a1 and b1): Modeled electrode-sponge finite element geometry. The head model comprised of 4 concentric blocks (skin, skull, CSF, brain). The electrode and sponge pad had 0.5 and 2.5 mm thickness, respectively. 2 mA of total current was applied to 35 cm2 pads (boundary current density 0.0057 A/m2). (a2 and b2): For saline soaked sponge (1.4 S/m), current density was concentrated at electrode edges, with higher values observed at the rectangular electrode corners. Both panels plotted to the peak current density for the rectangular electrode (0.041 A/m2). (a3 and b3): Re-plotting these panels to a maximum current density of 0.029 A/m2, emphasize that outside of the rectangular electrode corners, the typical current density around the circular electrode is higher. (a4 and b4): Decreasing sponge salinity (0.05 S/m) resulted in significantly more uniform electrode current densities, and reduced peak current densities for both rectangular and circular pads to approximately the same values Comparison of the skin current density profiles for area matched rectangular and circular pads
  15. 15. Electrode montage in stroke Findings: •Bilateral tDCS, anodal tDCS and cathodal tDCS were shown to be associated with significant improvements on the JTT. •Bilateral and extra-cephalic stimulation do not induce effects on motor function •Effects of tDCS are task-dependent and might be different for neuropsychiatric conditions, such as stroke Changes in the main outcome (Jebsen–Taylor Hand Motor Function Test – as measured in seconds) in each electrode montage. Columns indicate mean changes and bars indicate standard error of the mean.
  16. 16. Summary Note on tDCS Brain function under the anodal electrode site is enhanced by roughly 20 to 40% when the current density (concentration of amperage under the electrode) exceeds 40 μA/cm2 (260 μA/inch2). The cathode reduces brain function under the electrode site by 10 to 30% at the fore-mentioned current density. Anodal stimulation is the most common form of tDCS as most applications require enhanced brain function.

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