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Transcranial Direct Stimulation Shows Improvement in Patients With Post-Stroke Aphasia

Patients administered A-tDCS during outpatient speech therapy were shown to have a relative increase of 70% in correct-naming for A-tDCS compared to sham.

Julius Fridriksson, PhD

Anodal transcranial direct current stimulation (A-tDCS), when used in combination with speech therapy has shown positive outcomes for patients with post-stroke aphasia.

Compared to sham tDCS, patients administered A-tDCS during outpatient speech therapy were shown to improve in correct naming exercises by 5.7 (standard error [SE], 3.3) more words (95% CI, -0.9 to 12.3), for a relative increase of 70% in correct-naming for A-tDCS compared to sham.1

Led by Julius Fridriksson, PhD, the co-director of the McCausland Center for Brain Imaging and the director of the Center for the Study of Aphasia Recovery in the Arnold School of Public Health, at the University of South Carolina, in Columbia, the double-blind, prospective, randomized trial explored the effects of A-tDCS in 74 patients with a mean age of 60 (standard deviation [SD], 10) and a mean of 44 (SD, 40) months from stroke onset. The most common type of aphasia was broca aphasia, occurring in 52.7% of patients (n = 39).

“Chronic aphasia is very resistant to treatment. Our study suggests that adjuvant A-tDCS may boost the effect of behavioral language therapy of stroke patients with aphasia,” Fridriksson told NeurologyLive. “Although this was not a definitive study, it provides strong evidence to foster more research on this topic. Ultimately, A-tDCS may offer a new way to enhance the effect of the behavioral therapy of aphasia.”

Patients were randomized to either A-tDCS (n = 34) or sham (n = 40), with all of them set to receive a conjunctive computerized speech task, depicting common objects visually displayed paired with words heard audibly. The therapy was administered over the course of a 15-session, 3-week period.

The adjusted mean (SE) change after 1 week of therapy was 13.9 (2.4; 95% CI, 9.0 to 18.7) items correctly named for the A-tDCS group compared to 8.2 (2.2; 95% CI, 3.8 to 12.6) for the sham group. The unadjusted, computers-only analysis (which excluded 2 patients with hemorrhagic stroke who were erroneously enrolled in the trial) revealed consistent data of the entire intent-to-treat population (test of H0: μA − μS ≥1.5; t statistic, 1.35; 1-sided P = .91). Similarly, a sensitivity analysis also revealed consistent findings (test of H0: μA − μS ≥1.5; t statistic, 1.2; 1-sided P = .89).

After 4 weeks of treatment, the adjusted mean (SE) of change in words correctly named was 16.8 (2.8; 95% CI, 11.3 to 22.4) for the A-tDCS group and 9.4 (2.5; 95% CI, 4.4 to 14.5; 1-sided P = .94). The results seemed to hold through 24 weeks posttreatment, as well, with the adjusted mean (SE) change from baseline in correct naming being 14.9 (3.7; 95% CI, 8.8 to 21.1) for the A-tDCS group compared to 7.1 (3.3; 95% CI, 1.59 to 12.0) for the sham group (1-sided P = .90).

“We had completed 2 phase I studies to study adverse event rates and provide an effect size to motivate the trial,” Fridriksson said. “There are also several other phase I studies that had suggested A-tDCS might be a feasible mechanism to boost the effect of stroke/aphasia treatment.”

The therapy was well-tolerated, with 1 patient in each group (3% overall) not undergoing all 15 sessions—the patient in the A-tDCS group opted out after session 11, and the patient in the sham group experienced a seizure during the trial, prompting discontinuation. In total, 8 mild, non-serious adverse events occurred, with no statistical differences between treatment groups. Erythema occurred in 6% (n = 2) of patients in the A-tDCS group compared to none in the sham group. Using the Wong-Baker FACES Pain Rating Scale, individuals most often reported no hurt—this being the case in 94% (n = 476) of those in the A-tDCS group compared to 86% (n = 511) in the sham group. The highest pain rating observed was 3, indicating “hurts even more,” which was reported 4 times by 2 individuals (3%), both in the sham group.

In an accompanying editorial comment,2 Steven C. Cramer, MD, MMSc, asked “what does the ability to name 13.9 more objects mean in real life? If you are trying to order lunch or select a grandchild’s birthday present, it can mean the world. If you are litigating a criminal case, it is likely insufficient. For most patients, this improvement may be clinically important.” Fridriksson and colleagues wrote that “even 1 to 2 words’ improvement could be meaningful to some patients who have very limited speech output.”

Fridriksson and colleagues noted that given that the trial failed to reject the null hypothesis, the results suggested that a larger trial may be warranted for further evaluation. “More work is needed to verify the effect revealed in our trial,” Fridriksson told NeurologyLive. “We also need to better understand the proper dose and patient characteristics related to outcome. We are planning a follow-up trial to replicate our findings and explore optimal dosage.”

As for future trials, Cramer noted that “the global outcome measures found useful in acute stroke studies, such as the modified Rankin Scale, would be insensitive to most behavioral gains provided by the current intervention, underscoring the importance of modality-specific endpoints in restorative stroke trials.”


1. Fridriksson J, Rorden C, Elm J, et al. Transcranial Direct Current Stimulation vs Sham Stimulation to Treat Aphasia After Stroke: A Randomized Clinical Trial. JAMA Neurol. Epub August 20, 2018.



2. Cramer SC. Stimulating Dialogue Through Treatment of Poststroke Aphasia With Transcranial Direct Current Stimulation. JAMA Neurol. Epub August 20, 2018.