Examining Chronic Post-Stroke Aphasia Recovery Using Non-Invasive Brain Stimulation and Neuroimaging
Date
2024-06-24
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Abstract
Aphasia, an impairment in language processing, affects approximately one-third of stroke survivors immediately after stroke and up to 50% will have long-term impairments. Rehabilitation of aphasia at the chronic phase is possible, though outcomes are variable and often minimal. Novel therapeutic approaches and an increased understanding of the neurobiology supporting recovery are needed. Chapter Two assessed the safety and feasibility of combining repetitive transcranial magnetic stimulation (rTMS) with high-intensity Multi-Modality Aphasia Therapy (M-MAT) in chronic post-stroke aphasia (n=20). This novel combination therapy was determined to be feasible and safe in chronic post-stroke aphasia. On the basis of all participants benefiting from M-MAT regardless of rTMS allocation, we used resting-state fMRI (Chapter Three) and diffusion-weighted MRI (Chapter Four) to examine functional and structural connectivity associated with changes in speech production. In individuals that made positive, significant changes in naming, pre-treatment functional and structural connectivity of left hemisphere temporal and parietal language regions were associated with greater treatment-related improvement in naming. Additionally, naming improvements were associated with decreases in functional connectivity of bilateral posterior temporoparietal regions with frontoparietal, sensorimotor and visual networks at post-treatment. In Chapter Five, we conducted a randomized controlled trial investigating the efficacy of rTMS plus M-MAT on aphasia severity in a larger cohort of chronic stroke participants (n=43). Delivery of rTMS combined with M-MAT resulted in significant supplemental improvements in aphasia severity compared to sham plus M-MAT at follow-up. This demonstrates that rTMS is a promising adjuvant therapy for M-MAT in chronic stroke. Chapter Six investigated the neural basis of adjuvant rTMS effects using overt naming fMRI. Participants who received rTMS with M-MAT demonstrated dynamic functional reorganization over time, resulting in increased recruitment of left hemisphere perisylvian and temporoparietal regions at 15 weeks compared to sham. These data demonstrate potential mechanisms for the behavioural improvements observed following rTMS plus M-MAT. This thesis provides evidence to support the efficacy of rTMS plus M-MAT for improving chronic post-stroke aphasia. In addition, this thesis advances our understanding of the structural and functional brain architecture that supports aphasia recovery. These behavioural and neuroimaging results are important for the advancement of post-stroke aphasia rehabilitation.
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Keywords
Aphasia, Stroke rehabilitation, Transcranial magnetic stimulation, Speech language therapy, Magnetic resonance imaging
Citation
Low, T. A. (2024). Examining chronic post-stroke aphasia recovery using non-invasive brain stimulation and neuroimaging (Doctoral thesis, University of Calgary, Calgary, Canada). Retrieved from https://prism.ucalgary.ca.