Dissociation of white matter bundles in different recovery measures in post-stroke aphasia

BackgroundPost-stroke aphasia (PSA) recovery shows high variability across individuals and at different moments during recovery. Although diffusion biomarkers from the ventral and dorsal streams have demonstrated strong predictive power for language outcomes, it is still unclear how these biomarkers relate to the various stages of PSA recovery. In this study, we aim to compare diffusion metrics and language measures as predictors of language recovery in a longitudinal cohort of participants with PSA. MethodsTwenty-four participants (mean age = 73 years, 8 women) presenting PSA were recruited in an acute stroke unit. Participants underwent diffusion MRI scanning and language assessment within 3 days (acute phase) after stroke, with a behavioral follow-up at subacute (10{+/-}3 days) and chronic phases (> 6 months). We used regression analyses on language performance (cross-sectional) and {Delta}scores at subacute and chronic timepoints (difference between acute and subacute, and subacute and chronic respectively), with language baseline scores, diffusion metrics from language-related white matter tracts, lesion size and demographic predictors. ResultsBest prediction model of performance scores used axial diffusivity (AD) from the left arcuate fasciculus (AF) in both subacute (R2 = 0.785) and chronic timepoints (R2 = 0.626). Moreover, prediction of change scores depended on AD from left inferior frontal-occipital fasciculus (IFOF), in subacute stage (R2 = 0.5), and depended additionally on AD from right IFOF in the chronic stages (R2 = 0.68). Mediation analyses showed that lesion load of left AF mediated the relationship between AD from left AF and chronic language performance. ConclusionLanguage performance in subacute and chronic timepoints depends on the integrity of left AF, whereas {Delta}scores of subacute and chronic phases depends on left IFOF, showing a dissociation of the white matter pathways regarding language outcomes. These results support the hypothesis of a functional differentiation of the dual-stream components in PSA recovery.