Transcranial Direct Current Stimulation to Treat Aphasia: A Superiority Study - Abstract Stroke is one of the leading causes of disability worldwide. The National Institute on Deafness and Other Communication Disorders estimates that approximately 2 million people suffer from post-stroke chronic language problems (aphasia) in the United States. The standard treatment for chronic aphasia is speech therapy. However, the outcomes of speech therapy for chronic aphasia are often unsatisfactory, underscoring the need for advancements in therapeutic options. Transcranial direct current stimulation (tDCS) has recently emerged as a promising method that can have synergistic effects when applied concurrently with speech therapy, significantly improving language outcomes. However, despite the potential transformative effect of tDCS as an adjuvant treatment for chronic aphasia, the existing literature is composed by small sample sizes or uncontrolled studies. From an evidence-based medicine perspective, these studies do not constitute Level 1 evidence and are not sufficient to prove superiority and justify the translation of tDCS to clinical use. Hence, a definitive Level 1 evidence study is strongly needed and this application addresses this critical knowledge gap. Our team has conducted the largest preliminary futility design clinical trial in tDCS and aphasia, in which we formally demonstrated that a definitive superiority clinical trial to assess adjuvant tDCS coupled with auditory-visual speech is feasible, warranted, and not futile. Leveraging this formal and rigorous foundation, this project will be a prospective randomized controlled clinical trial to compare auditory-visual speech therapy coupled with adjuvant active anodal tDCS (A-tDCS) versus speech therapy coupled with sham tDCS (S-tDCS). We will perform an adaptive Phase II/III design, in which the first portion of the study (Phase II) will determine the optimal dose of A-tDCS (1 mA versus 2 mA) and provide a go/no-go decision for Phase III. Phase III will test the definitive superiority of adjuvant A-tDCS at the optimal dose coupled with speech therapy versus speech therapy alone (S-tDCS) to improve naming among individuals with chronic Broca’s aphasia. The primary outcome measure will be the number of individuals who achieve a meaningful improvement in naming from baseline to 4 weeks post-therapy. Improvement in aphasia severity, communication confidence, discourse, and quality of life will be evaluated as secondary outcome measures. This project stands to be the first efficacy trial of tDCS for aphasia, paving the way for a new clinical treatment that would directly benefit patient care. By focusing on naming deficits in Broca’s aphasia, this trial will address a significant aspect of aphasia and lay the groundwork for future studies exploring tDCS applications for various types and stages of aphasia, ultimately enhancing the standard of care for millions affected by this condition.
