The efficacy of NIBS in aphasia treatment: Promising but patient- and stimulation-specific results

Abstract

Aphasia constitutes one of the most serious language disorders. Over the past decades, non-invasive brain stimulation (NIBS) has emerged as a possible treatment tool, on its own or to augment proven methods, such as speech and language therapy (SLT). However, studies relying on NIBS have exhibited rather varying results and small sample sizes, urging for a comprehensive analysis of a greater amount of data to establish a clearer assessment. Thus, this thesis is concerned with determining the efficacy of NIBS for treating post-stroke aphasia (PSA) and primary progressive aphasia (PPA).To address this gap, a qualitatively driven meta-analysis was conducted to evaluate the language-related effects of transcranial direct current stimulation (tDCS) and transcranial magnetic stimulation (TMS). Therefore, published studies on tDCS and TMS in the treatment of PSA and PPA were collected, and inductive coding was employed to not only capture the effectiveness, but also its relation to patient- and stimulation-related parameters. While the results were not entirely uniform, they did show a promising efficacy of tDCS and TMS as aphasia treatment, particularly in the context of PPA treatment. Furthermore, a crucial benefit was that this approach enabled the establishment of a more holistic evaluation, highlighting the likely dependency of the efficacy on specific patient-related parameters (e.g., volume of specific neuroanatomical structures, sleep efficiency). Overall, it demonstrated that NIBS can be a promising tool in the treatment of aphasia especially to augment SLT.