Research Highlights:
- Neither a placebo procedure nor two different doses of transcranial brain stimulation, which send electrical signals through the skull, improved mobility recovery in stroke survivors receiving movement therapy.
- Motor function was similar among survivors who received electrical brain stimulation combined with movement therapy or a placebo combined with movement therapy.
- Note: The study featured in this news release is a research abstract. Abstracts presented at the American Heart Association's scientific meetings are not peer-reviewed, and the findings are considered preliminary until published as full manuscripts in a peer-reviewed scientific journal.
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:
- Transcranial direct current stimulation up to 4mA did not amplify the effect of constraint-induced movement therapy.
- 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.
- The stimulation is safe and tolerable in stroke patients. The combined intervention was feasible to implement in the multi-center clinical trial setting.
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:
- Study participants were first-ever ischemic (clot-caused) stroke survivors who suffered a stroke one to six months earlier and had persistent arm weakness but still had slight movement of the hand.
- The study included 129 stroke survivors with an average age of 59 years. 42% were women, 53% were white adults, 41% were Black adults, 3% were Asian population and about 2% said they were multiple races. Participants were randomly assigned to one of three doses of brain stimulation.
- It was conducted between September 2019 and September 2024 in 15 U.S. medical centers in 11 U.S. states and the District of Columbia. Each person participated in the study for about four months.
- Clinical outcome was assessed using the Fugl-Myer Upper-Extremity Scale (measuring motor impairment), Wolf Motor Functional Test (measuring motor function) and the Stroke Impact Scale Hand Subscale (measuring quality of life).
- All clinical outcomes were assessed immediately after two weeks of intervention, and again one month and three months after the initial intervention.
- Researchers found the combined brain stimulation and intensive rehabilitation therapy was safe, tolerable and feasible.
- Feng led the study with co-principal investigator Gottfried Schlaug, M.D., Ph.D., FAHA., vice-chair for Research at University of Massachusetts Chan Medical School – Baystate in Springfield. Additional study co-authors, funding and disclosures are available in the abstract.
Statements and conclusions of studies that are presented at the American Heart Association's scientific meetings are solely those of the study authors and do not necessarily reflect the Association's policy or position. The Association makes no representation or guarantee as to their accuracy or reliability. Abstracts presented at the Association's scientific meetings are not peer-reviewed, rather, they are curated by independent review panels and are considered based on the potential to add to the diversity of scientific issues and views discussed at the meeting. The findings are considered preliminary until published as a full manuscript in a peer-reviewed scientific journal.
