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Frontal callosal microstructure and longitudinal recovery of comprehension and production after stroke
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Poster E50 in Poster Session E, Thursday, October 26, 10:15 am - 12:00 pm CEST, Espace Vieux-Port
Veronika Vadinova1, Aleksi Sihvonen1, Kimberley Garden1, Katie McMahon2, David Copland1, Sonia Brownsett1; 1University of Queensland, 2Queensland University of Technology
Introduction: The frontal segment of the corpus callosum forceps minor (F-minor) is highly susceptible to microstructural deterioration in aging1,2, and measures of its integrity have been successful in explaining cognitive heterogeneity in healthy aging1-4, neurodegeneration5,6, and stroke7. The potential prognostic role of frontal callosal microstructure has been neglected in aphasia research. Given the hypothesized role of callosal connections in enabling right-hemisphere compensation after stroke8, reduced microstructure within F-minor may hinder optimal engagement of compensatory networks and have a detrimental impact on language recovery. Aims: Here, we aimed to investigate the extent to which the early subacute microstructure of the F-minor contributes to longitudinal outcomes in poststroke aphasia. We hypothesized, based on findings in healthy ageing1,3,4 and disease5,6, that a region-wise averaged radial diffusivity of F-minor (RD F-minor) would explain variance in longitudinal language comprehension and production after stroke. Methods: 32 individuals with aphasia were included at baseline (<6 weeks), and 25 of these completed the chronic assessment (6 months). Spoken language comprehension and production abilities were assessed at both timepoints using word and sentence-level tasks. All neuroimaging data was acquired at the early subacute stage (<6 weeks). T1-weighted MRI sequences were used to calculate overall percentage of stroke lesion load within the F-minor. Diffusion magnetic resonance imaging (dMRI) data was pre-processed using MRTrix (www.mrtrix.org), F-minor was automatically reconstructed in DSI Studio (http://dsi-studio.labsolver.org) and RD in F-minor metric was extracted. Stepwise multiple regression models were used to test if percentage stroke lesion load and RD in F-minor, together with demographic variables (age, sex, education), explained variance in outcomes at both timepoints. Chronic models likewise controlled for early subacute performance. Results: Spoken Comprehension: At early subacute stage only age, percentage stroke lesion load and sex explained variance in spoken comprehension (model statistics: R2 = .59, F(3, 28) = 13.68, p < .001). RD in F-minor did not explain additional variance (p = .08). At the chronic timepoint, education, early subacute scores and RD in F-minor explained variance in spoken comprehension (β = -44.37, t = -4.88, p < .001) (model statistics: R2 = .82, F(3,21) = 33.25, p < .001). Spoken Production: at the early subacute stage, only RD in F-minor explained variance in outcomes (β = -82.20, t = -2.38, p = .024) (model statistics: R2 = .17, F(1, 27) = 5.67, p = .024). At the chronic timepoint, only early subacute scores explained variance in outcomes (model statistics: R2 = .83, F(2,19) = 48.48, p < .001). RD in F-minor did not explain additional variance (p = .37). Discussion: We provide initial evidence that early subacute microstructure in frontal callosal connections could serve as an independent biomarker of comprehension and production outcomes after stroke. The differential relationship between callosal microstructure over time and different aspects of language highlights the need for detailed consideration. By leveraging early subacute dMRI data (<6 weeks), to minimize the extent of stroke-induced secondary degeneration9, our study demonstrates the importance of pre-stroke callosal microstructure in language recovery after stroke.
Topic Areas: Disorders: Acquired, Speech Perception