Strokes occur when blood supply to a part of the brain is blocked by something or when a blood vessel located in the brain bursts. Damage to the brain results from a stroke. Stroke is the second leading cause of death worldwide, following heart disease. It is also the leading cause of disability worldwide. The risk of stroke increases with age. Although about 80% of stroke patients survive, survivors encounter a negative impact on their quality of life. This is due to stroke symptoms that include motor impairments, loss of coordination, and limb hemiparesis. Recovery from stroke can be difficult due to many clinical factors, including the formation of glial scars that prevent axon regeneration. Task-oriented training, such as physical therapy can help with motor rehabilitation, but physical therapy alone is not enough. Electrical stimulation provides a more targeted approach to motor rehabilitation and may produce better results. Electrical stimulation can cause changes in neuroplasticity, effectively rewiring the brain and improving motor capability.
The review article, Rewiring the Lesioned Brain: Electrical Stimulation for Post-Stroke Motor Restoration, by Bao et al., gives an overview of current electric stimulation methods and their mechanisms and discusses the future of electrical stimulation concerning stroke recovery. The article describes two categories of electrical stimulation: noninvasive brain stimulation (NIBS) and peripheral electrical stimulation. NIBS is often used as a supplementary tool in stroke recovery. It continues to modulate brain plasticity even after the stimulation period. This can further enhance the motor function of affected limbs. NIBS includes transcranial direct current stimulation (tDCS), transcranial magnetic stimulation (TMS), and cerebellum and spinal cord stimulation. Peripheral electrical stimulation has also shown promise regarding stroke recovery. The two forms of peripheral electrical stimulation discussed in the article were neuromuscular electrical stimulation (NMES) and transcutaneous electrical nerve stimulation (TENS). Although stroke patients cannot voluntarily move limbs affected by the stroke, their spinal motor neurons are intact and can be excited by NMES. NMES can modulate neuron hyperpolarization and depolarization and excite peripheral nerves. The article also discusses other forms of invasive electrical stimulation that have emerged recently, but need to be studied further. Deep brain stimulation, which stimulates electrodes that are implanted in deep regions of the brain, can stimulate impaired neural circuits, facilitating reorganization and improving plasticity.
Investigating one of the two categories of electrical stimulation discussed in the review article, Chen et al.’s Effects of 8-week sensory electrical stimulation combined with motor training on EEG-EMG coherence and motor function in individuals with stroke utilizes peripheral electrical stimulation to study its effects on chronic stroke patients’ neuromuscular control and hand function. The study involved twelve subjects who were either assigned to the control group or received electrical stimulation. The groups received twenty minutes of hand function training twice a week, and the subjects that were not part of the control group also received 40-minute sessions of electrical stimulation before each biweekly training session. The subjects were assessed before the experiment, on the fourth and eighth week of the experiment, and four weeks after the conclusion of the experiment, as a follow-up. Subjects who received electrical stimulation showed significant improvement in corticomuscular control at the four-week mark compared to subjects who received sham electrical stimulation. The article mentioned that recovery for patients afflicted with chronic stroke was more difficult than that of patients with a more recent stroke. However, this study was able to show improvement in corticomuscular control even in chronic stroke patients.
Although the exact mechanisms of stroke recovery through electrical stimulation are not completely understood yet, it has shown much promise in future treatments. In conjunction with physical therapy, much improvement can be observed. With further research into the newer methods mentioned in Bao’s review article and the peripheral electrical stimulation investigated in Chen’s experiment, stroke recovery can be made more efficient and effective. Together, the two articles show the potential of electrical stimulation for stroke survivors and point toward further research.
References:
1. Bao S. Rewiring the Lesioned Brain: Electrical Stimulation for Post-Stroke Motor Restoration
J Stroke. 2020 Jan 31. doi: https://doi.org/10.5853/jos.2019.03027.
2. Pan LH, Yang WW, Kao CL, Tsai MW, Wei SH, Fregni F, Chen VC, Chou LW. Effects of 8-week sensory electrical stimulation combined with motor training on EEG-EMG coherence and motor function in individuals with stroke. Sci Rep. 2018 Jun 15;8(1):9217. doi: 10.1038/s41598-018-27553-4.
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