Research Highlights:
Embargoed until 11:30 a.m. PT/2:30 p.m. ET Thursday, Feb. 6, 20 25
LOS ANGELES, Feb. 6, 2025 — Mild electrical brain stimulation did not further improve motor recovery in stroke survivors, according to late-breaking science presented today at the American Stroke Association’s International Stroke Conference 2025 . The conference, in Los Angeles, Feb. 5-7, 2025, is a world premier meeting for researchers and clinicians dedicated to the science of stroke and brain health.
“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.”
In the United States, stroke is the fifth leading cause of death and a leading cause of long-term disability, according to the American Heart Association’s Heart Disease and Stroke Statistics 2025 Update , released last week. Depending on the part of the brain affected, stroke may impair arm and/or leg movement and activities of daily life among survivors. Motor impairment (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.
Researchers studied 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 4 milliamps (4 one thousandth of an ampere) powered by a 9-volt battery — was delivered through the skull.
The study, TRANScranial direct current stimulation for POst-stroke motor Recovery — a phase II sTudy (TRANSPORT 2), is the first funded multi-center stroke recovery study on the National Institutes of Health (NIH) StrokeNet, a network of U.S. regional centers 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 (2 milliamps) and higher dose (4 milliamps or mA) — on 129 stroke survivors undergoing constraint-induced movement therapy in major medical centers across the U.S. The stimulation was 30 minutes and the CIMT therapy was 120 minutes each session.
The analysis found:
A 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 enrollment 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 4 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.”
Study design, background and details:
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About the American Stroke Association
The American Stroke Association is devoted to saving people from stroke — the No. 2 cause of death in the world and a leading cause of serious disability. We team with millions of volunteers to fund innovative research, fight for stronger public health policies and provide lifesaving tools and information to prevent and treat stroke. The Dallas-based association officially launched in 1998 as a division of the American Heart Association. To learn more or to get involved, call 1-888-4STROKE or visit stroke.org . Follow us on Facebook , X .
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