Efficacy of rTMS in Post-Stroke Bilingual Aphasia: A Single Case Experimental Design

The application of non-invasive brain stimulation in the rehabilitation of bilingual individuals with aphasia following a stroke is understudied. Recent studies show benefits of anodal cerebellar transcranial Direct Current Stimulation in bilinguals, while in monolinguals, repetitive Transcranial Magnetic Stimulation (rTMS) targeting the motor cortex of the lips seems to be effective in aphasia recovery.

We aimed to investigate the effects of inhibitory continuous theta burst rTMS stimulation targeting the right motor cortex of the lips during picture naming task in the second language of a French-English post-stroke bilingual individual.

We enrolled a single bilingual (PR) exhibiting chronic post-stroke aphasia in both her second language (L2), and first language (L1). In the present study PR engaged in naming tasks three times a week for six weeks, including 2-week baseline, 2-week intervention and 2-week follow-up.

The results demonstrated a statistically significant improvement in naming accuracy in the second language of the patient, as evidenced by visual analysis in both cognate and non-cognate words, as well as, overall language accuracy. Visual analysis revealed a positive improvement in all variables, with the greatest improvements observed in phonology, overall accuracy, and pathological language switching.

The stimulation of the motor cortex of the lips resulted in an improvement in naming accuracy in both the first and second language of the participant, despite the possible varying language recovery after stroke. This suggests the possible existence of shared representations of language in the brain, which is likely due to the similarities between the languages. Further studies are required to confirm the efficacy of non-invasive brain stimulation in bilingual individuals with aphasia for deeper understanding of the underlying mechanisms influencing these outcomes.

What is already known on this subject The application of non-invasive brain stimulation in bilinguals with post-stroke aphasia is understudied. Studies have indicated that the cortical organization of each language in bilingual individuals may exhibit overlap particularly in the case of similar languages, leading to a pathological language switching following cerebral lesions. A study by Coemans et al. (2023) demonstrated the efficacy of cerebellar transcranial direct current stimulation in bilingual individuals. The objective of this study is to investigate the effects of transcranial magnetic stimulation during a naming task on the second language of a post-stroke bilingual aphasia individual and to gain insight into the cortical organisation of each language. What this study adds to existing knowledge The present study demonstrates the potential of inhibitory repetitive transcranial magnetic stimulation (rTMS) targeting the right motor cortex of the lips to enhance picture naming accuracy in both languages and reduce pathological language switching in bilingual individuals with aphasia. The results demonstrate that rTMS not only facilitates recovery in each language but also has a beneficial impact on the cognitive control mechanisms involved in language switching, particularly for cognate words. That suggests that rTMS impacts both the targeted motor areas and broader cognitive networks, thereby providing insights into the bilingual language recovery process and highlighting the benefits of rTMS in bilingual aphasia. What are the clinical implications of this study? The clinical implications of this study indicate that rTMS may serve as a valuable tool for enhancing naming abilities and, consequently, language abilities in bilingual patients, particularly when the two languages exhibit similarities. The results suggest that rTMS targeting the motor cortex of the lip has the potential to simultaneously address linguistic and cognitive aspects of bilingual aphasia by targeting the phonological pathway and brain regions involved in cognitive control and language selection. These findings may assist clinicians in the development of personalized rehabilitation strategies for bilingual individuals with post-stroke aphasia.