Safety and tolerability of transcranial direct current stimulation for persons with aphasia: a randomized controlled pilot trial

Background Combining transcranial direct current stimulation (tDCS) with conventional speech-language therapy (SLT) has gained attention in aphasia rehabilitation. However, evidence from low- and middle-income countries, including India, is limited, and safety concerns persist for persons with aphasia (PWA). Although tDCS is generally considered safe, few studies have systematically evaluated its safety and tolerability in this population.Aims This pilot study aimed to evaluate the safety and tolerability of tDCS combined with SLT in persons with aphasia in India.Methods and Procedures A single-centre, double-blinded, randomized, placebo-controlled pilot trial was conducted. Twenty Kannada-speaking individuals with post-stroke aphasia were randomised into active tDCS (A-tDCS) and sham tDCS (S-tDCS) groups. Participants received 15 sessions over 15 days, followed by a 15-day follow-up. The protocol included 1 mA stimulation for 20 minutes, combined with 1 hour of SLT. Safety was assessed using reported adverse events (AEs), and tolerability was measured using a pain rating scale. Reporting followed CONSORT guidelines.Outcomes and Results Of 48 individuals screened, 27 were randomized, 20 completed treatments and 5 were lost to follow-up. Reported AEs were mild, with tingling and pricking sensations most common in both groups. Although a significant difference in AEs was observed between groups, all events were transient and non-persistent. Tolerability scores were below 4/10 in both groups, with no significant group differences.Conclusions This pilot study provides quantitative evidence of the safety and tolerability of tDCS combined with SLT in PWA, and supports the feasibility of larger clinical trials.