Mild electrical brain stimulation did not further improve motor recovery in stroke survivors, according to the results of what researchers say is a surprising study.
Motor impairment, such as arm and/or leg weakness, is the most common complication after stroke.
Constraint-induced movement therapy (CIMT) restricts movement on the unaffected arm by wearing a mitt over a hand to force the use of the stroke-affected side. This therapy has been shown to improve motor function and quality of life in certain stroke patients with preserved hand movement.
However, it requires intensive treatment. For example, the traditional format requires six hours per day and a modified treatment format requires two hours per session in the clinic, five days per week, with additional homework after the clinical session. This can be challenging for stroke survivors, Feng said.
For this study, researchers examined whether transcranial direct current stimulation could enhance the effects of constraint-induced movement therapy, allowing for better use of the arm affected by the stroke. In this study, a weak electrical current — up to four milliamps (four one thousandth of an ampere) powered by a nine-volt battery — was delivered through the skull.
“The results are somewhat surprising to us,” said study leading-principal investigator Wayne Feng, M.D., M.S., professor of neurology and biomedical engineering at Duke University School of Medicine in Durham, North Carolina.
“We initially hoped that a higher dose at 4 milliamps electrical stimulation had a better effect than a lower dose as well as the sham group, but we did not see that.”
The sTudy, TRANScranial direct current stimulation for POst-stroke motor Recovery — a phase II sTudy (TRANSPORT 2), is the first funded multi-centre stroke recovery study on the National Institutes of Health (NIH) StrokeNet, a network of U.S. regional centres and hospitals conducting major stroke-related clinical trials focusing on acute treatment, prevention and recovery.
Researchers assessed three aspects of arm function (impairment, function and quality of life) after 10 sessions over the two-week period using three doses of electrical stimulation — sham/placebo stimulation, low dose (two milliamps) and higher dose (four milliamps or mA) — on 129 stroke survivors undergoing constraint-induced movement therapy.
The stimulation was 30 minutes and the CIMT therapy was 120 minutes each session.
Findings
The analysis found that transcranial direct current stimulation up to 4mA did not amplify the effect of constraint-induced movement therapy, and that the stroke survivors in all three groups improved after two weeks of treatment, and the effect continued at one month and three months after the intervention. However, the magnitude of improvement among the three groups was similar.
It further found that the stimulation is safe and tolerable in stroke patients.
The researchers highlight that the limitation of the study is the trend of uneven representation of women in each group considering that women may respond differently than men to brain stimulation.
Another limitation is that the study was interrupted by the COVID-19 pandemic, which slowed enrolment and scoring issues on the primary outcomes.
“In future clinical trials, we plan to enhance our approach by implementing several improvements,” Feng said.
“These improvements will include using a higher dose – more than four milliamps, ensuring men and women are equally distributed in each group and ensuring consistent administration and scoring the primary outcomes across all clinical trial sites. It may take us a few attempts before we achieve success.”
