The latest findings from a Phase 2 clinical trial have revealed that transcranial direct current stimulation (tDCS) failed to provide additional motor recovery benefits for post-stroke patients when combined with conventional rehabilitation therapy. The results were presented at the 2025 International Stroke Conference in Los Angeles, California.
The TRANSPORT 2 trial (TRANScranial direct current stimulation for POst-stroke motor Recovery — a phase II sTudy) enrolled 129 patients who had experienced an ischemic stroke within the previous 1-6 months and retained partial hand movement capability. The study population was diverse, with an average age of 59 years and included 42% women, 53% White, 41% Black, and 3% Asian participants.
Trial Design and Implementation
Researchers conducted the study across 15 U.S. medical centers between September 2019 and September 2024. Participants were randomized to receive either sham treatment, low-dose (2mA), or high-dose (4mA) electrical stimulation in conjunction with constraint-induced movement therapy (CIMT) over a two-week period, consisting of 10 sessions.
The research team employed multiple assessment tools to evaluate outcomes, including the Fugl-Myer Upper-Extremity Scale, Wolf Motor Functional Test, and the Stroke Impact Scale Hand Subscale. Patient progress was monitored through follow-up assessments at one and three months post-treatment.
Key Findings and Implications
"The results are somewhat surprising to us," stated lead investigator Wayne Feng, MD, MS, professor of neurology and biomedical engineering at Duke University School of Medicine. "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."
While all treatment groups demonstrated improvement following the two-week intervention period, with sustained gains at both one-month and three-month follow-ups, there were no significant differences in recovery magnitude between the groups. Importantly, the study confirmed that the stimulation procedure was safe and well-tolerated across all dosage levels.
Study Limitations and Future Directions
The investigation faced several notable challenges, including:
- Uneven gender distribution across treatment groups, which may have influenced response patterns to brain stimulation
- COVID-19-related disruptions affecting enrollment rates
- Inconsistencies in primary outcome scoring across sites
Dr. Feng outlined plans for future trials, emphasizing several key improvements: "We plan to enhance our approach by implementing several improvements. 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."
Despite the neutral results, researchers maintain that tDCS remains a viable option for stroke rehabilitation research, with future studies potentially exploring higher stimulation doses and more refined methodological approaches.
