TMS and tDCS in post-stroke aphasia: Integrating novel treatment approaches with mechanisms of plasticity

Aphasia is a common result of stroke, affecting over one million Americans. Currently, intensive speech therapy is the mainstay of treatment, although its efficacy has been variable at best. Recent years have seen the emergence of non-invasive brain stimulation, specifically Transcranial Magnetic Stimulation (TMS) and Transcranial Direct Current Stimulation (tDCS), as potential treatments for post-stroke aphasia. A growing body of investigations has shown the efficacy of both modalities in facilitating recovery from chronic aphasia, while data regarding subacute aphasia are much more limited and evidence in the acute post-stroke phase are still lacking. Much remains unknown about how these techniques cause clinical improvement or about their long-term efficacy, side-effects, and safety. In this article, we examine the data demonstrating the safety and efficacy of TMS and tDCS, discuss the major differences between them, and consider how those differences may inform the use of each modality. We also consider the different models of neuroplasticity in the setting of post-stroke aphasia and how these models may influence when and in which patients each modality would impart the most benefit.