Efficacy of Transcranial Magnetic Stimulation and Transcranial Direct-Current Stimulation in Primary Progressive Aphasia Treatment: A Review

Background: In recent years, there has been increasing interest in the application of repetitive Transcranial Magnetic Stimulation (rTMS) and transcranial Direct-Current Stimulation (tDCS) to enhance and rehabilitate the language abilities in individuals with neurodegenerative diseases. Objective: The aim of this narrative literature review is to investigate the usefulness of rTMS and tDCS to improve language abilities in people with Primary Progressive Aphasia (PPA). Methods: This narrative literature review was conducted through a search of the PubMed online database to identify studies investigating the effects of multiple sessions of rTMS or tDCS on language abilities in PPA patients, applied either as stand-alone interventions or in combination with language treatment. Results: Thirty-three studies fulfilled the inclusion criteria; five studies employed rTMS without language treatment; two studies applied tDCS as stand-alone intervention; twenty-two studies combined tDCS with language treatment; and four studies assessed the effects of tDCS during verbal task without language treatment. Conclusions: rTMS and tDCS applied with or without concomitant language treatment appear to be promising interventions for enhancing language abilities in PPA, with sustained effects reported over time. Further research is necessary to optimise stimulation protocols and to improve our understanding of their long-term effects. Moreover, randomised controlled trials (RCTs) with larger sample sizes are critically needed to clarify the true impact of brain stimulation in PPA, with a focus on changes in cognitive and functional performance, neural activity, and potential molecular correlates.