A stroke occurs when blood flow to part of the brain is cut off, preventing brain tissue from getting oxygen and nutrients. Strokes are the leading cause of disability in adults over the age of 55. Despite advances in medical care and rehabilitation, 35% of stroke patients still have difficulty performing daily tasks because they have trouble walking or standing. Approximately 70% of stroke patients have problems with walking, including slower walking speed, problems with coordination, and uneven stride length.
Doctors have found that these problems often occur when the pathways that spinal cord neurons use to transmit information from the brain to the body are disrupted. By applying electrical pulses to the brains of stroke patients, doctors have attempted to reactivate the neural pathways that control movement. Researchers have shown that electrical pulses to the brain can help stroke patients regain control of fine movements, but the ability to maintain basic walking patterns relies on neural pathways in the spinal cord. So a team of scientists from the US and Russia hypothesized that targeting the spinal cord could help stroke patients recover.
To test whether spinal cord electrical stimulation could help stroke patients walk again, the team attached electrodes to the skin of the patients' spinal cord. Transcutaneous Spinal Cord Stimulation or tSCS. Researchers have previously found that tSCS can help stroke patients walk more steadily and smoothly in the short term. But the team wanted to test whether tSCS could improve nerve and muscle function and help patients walk better in the long term.
To measure how tSCS affected the walking ability and muscle function of stroke patients, the researchers recruited two groups of four people each. Both groups of participants were matched for age, time since stroke, and walking speed to minimize experimental bias. All participants were over 18 years old, had experienced a stroke at least one year ago, and were able to walk without support. The researchers conducted gait training in both groups three times a week for eight weeks to improve balance and movement. The first group, called the control group, was assigned to only gait training, while the second group, called the stimulation group, was assigned to a combination of gait training and tSCS.
The researchers assessed how well each participant walked before, immediately after, and three months after walking training. The researchers measured each participant's step symmetry using two metrics: step length and stride length. They also measured participants' walking speed and the distance they walked in a six-minute period. The researchers collected this data through a combination of observation by physical therapists and direct measurements using sensor-equipped mats.
The team found that after gait training, the stimulation group's stride symmetry improved by 64%, while the control group's stride symmetry improved by only 33%. The stimulation group also had faster walking speeds and more consistent swing times than the control group. All participants in the stimulation group and one participant in the control group walked greater distances than they had before gait training, but only one participant in each group maintained this progress after three months. The researchers interpreted these changes as meaning that combining tSCS with gait training enabled stroke patients to walk faster and longer. However, they warned that patients could lose these gains if they did not continue treatment, as only gait symmetry showed a sustained improvement.
The researchers also measured changes in the participants' muscles and neurons before and after tSCS treatment and walking training. The researchers explained that the more complex and numerous a person's muscle groups are, the better they can control leg movements when walking. So they wanted to see how the patients' muscle groups work together when walking, i.e. Muscle synergy. To investigate muscle synergy, the researchers measured the activity of the leg muscles of five participants by attaching sensors to the participants' skin to detect electrical signals when the muscles contracted. The results showed that participants in the two stimulation groups had improved muscle coordination after walking and tSCS. The researchers interpreted this result as meaning that tSCS helped participants improve muscle coordination while walking.
The researchers concluded that electrical stimulation of the spinal cord allowed some stroke patients to walk better than before. However, they suggested that the effectiveness of tSCS could be improved with individualized training and customized stimulation settings to address each patient's challenges. They also suggested that studies be conducted for a longer period of time and with a larger number of participants to better understand the lasting effects of tSCS and to apply the findings to a wider range of stroke patients.
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