Recovery from aphasia in the first year after stroke

Abstract

Most individuals who experience aphasia after a stroke recover to some extent, with the majority of gains taking place in the first year. The nature and timecourse of this recovery process is only partially understood, especially its dependence on lesion location and extent, which are the most important determinants of outcome. The aim of this study was to provide a comprehensive description of patterns of recovery from aphasia in the first year after stroke. We recruited 334 patients with acute left hemisphere supratentorial ischemic or hemorrhagic stroke, and evaluated their speech and language function within 5 days using the Quick Aphasia Battery. At this initial timepoint, 218 patients presented with aphasia. Individuals with aphasia were followed longitudinally, with follow-up evaluations of speech and language at 1 month, 3 months, and 1 year post stroke, wherever possible. Lesions were manually delineated based on acute clinical MRI or CT imaging. Patients with and without aphasia were divided into 13 groups of individuals with similar, commonly occurring patterns of brain damage. Trajectories of recovery were then investigated as a function of group (i.e., lesion location and extent) and speech/language domain (overall language function, word comprehension, sentence comprehension, word finding, grammatical construction, phonological encoding, speech motor programming, speech motor execution, and reading). We found that aphasia is dynamic, multidimensional, and gradated, with little explanatory role for aphasia subtypes or binary concepts such as fluency. Patients with circumscribed frontal lesions recovered well, consistent with some previous observations. More surprisingly, most patients with larger frontal lesions extending into the parietal or temporal lobes also recovered well, as did patients with relatively circumscribed temporal, temporoparietal, or parietal lesions. Persistent moderate or severe deficits were common only in patients with extensive damage throughout the middle cerebral artery distribution, or extensive temporoparietal damage. There were striking differences between speech/language domains in their rates of recovery and their relationships to overall language function, suggesting that specific domains differ in the extent to which they are redundantly represented throughout the language network, as opposed to depending on specialized cortical substrates. Our findings have an immediate clinical application in that they will enable clinicians to estimate the likely course of recovery for individual patients, as well as the uncertainty of these predictions, based on acutely observable neurological factors.

Cerebral perfusion in post-stroke aphasia and its relation to residual language abilities

“…Overall, the results demonstrate that blood flow is reduced beyond the lesion site in chronic post-stroke aphasia and hypoperfused neural tissue in critical temporo-parietal language areas may not be fully able to support recovery. The findings underscore the critical and general role that left hemisphere posterior temporal regions play in various expressive and receptive language abilities (Ivanova et al, 2016; Ivanova, Zhong, Turken, Baldo, & Dronkers, 2021; Turken & Dronkers, 2011; Wilson et al, 2022). Overall, the study shows that slowed or reduced blood distribution can affect the functionality of regions beyond the lesion site and have a direct impact on behavioral outcomes.…”

“…The findings underscore the critical and general role that left hemisphere posterior temporal regions play in various expressive and receptive language abilities. 49,53–55 Overall, the study shows that slowed or reduced blood distribution can affect the functionality of regions beyond the lesion site and have a direct impact on behavioral outcomes.…”

Early white matter connectivity and plasticity in post stroke aphasia recovery

“…Due to the relatively small sample size, we were not able to study different patient subgroups separately. Although the covariate “old lesion load” (including old stroke lesion load) did not significantly contribute to any of the regression models, future (larger-scale) independent studies are crucial to validate our findings ( Poldrack et al, 2020 ) and could check whether the found effects hold or differ in various subgroups of patients ( Wilson et al, 2022 ), such as patients with and without stroke history, patients with different stroke types or language lateralization patterns.…”

Precision fMRI reveals that the language-selective network supports both phrase-structure building and lexical access during language production

“…The response to phrase-structure building demands (evidenced by a stronger response during sentence production than word-list production) was reliable in every language fROI. This distributed nature of phrase-structure building a) parallels the distributed effects of syntactic demands during language comprehension (e.g., Blank et al, 2016; Shain, Blank et al, 2020; Shain et al, in press), and b) aligns with evidence from aphasia, where damage to both frontal and temporal language areas and the white matter tracts connecting them can result in syntactic deficits (e.g., Kempler et al, 1991; Caplan et al, 1996; Dick et al, 2001; Wilson & Saygin, 2004; Mesulam et al, 2015; Wilson et al, 2022; see deBleser, 1987 for a discussion of earlier evidence), thus adding to the growing evidence against focal implementation of combinatorial linguistic processing. Importantly, we showed that the sentence > word-list effect in production cannot be explained by general cognitive demands.…”