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Poster E19, Friday, November 10, 10:00 – 11:15 am, Harborview and Loch Raven Ballrooms

Patterns of grey matter changes in the acute phase of post-stroke aphasia

Mariem Boukadi1,2, Karine Marcotte3,4, Maxime Montembeault1,2, Alex Desautels4, Simona Brambati1,2;1Department of Psychology, Université de Montréal, 2Centre de recherche de l’Institut universitaire de gériatrie de Montréal (CRIUGM), 3École d’orthophonie et d’audiologie, Université de Montréal, 4Centre de recherche de l’Hôpital du Sacré-Cœur de Montréal

Introduction: In the wake of a stroke, dynamic changes can take place in the brain beyond the primary lesion site and may contribute to the patterns of impairment or recovery of language in post-stroke aphasia (PSA). While there is extensive evidence of the functional reorganization of the language network in PSA, little is known about potential structural changes. Previous studies have found grey matter (GM) volume increases as well as decreases in regions remote from the primary lesion site in chronic stroke patients. These distant cortical effects have been attributed to secondary degeneration and reorganization, respectively. However, little is known about how early these changes can be observed post-stroke. The aim of this study was to determine whether remote GM changes are found in the acute phase (i.e., ≤ 3 days) of PSA. Methods: Data were obtained from 18 right-handed cognitively unimpaired controls (CTRL) and 9 PSA patients having suffered a first ischemic stroke in the left middle cerebral artery territory. The two groups were matched on age, sex, and education. All participants underwent a magnetic resonance imaging protocol including a T1 brain image using a 3T Skyra scanner. PSA patients were scanned within 3 days following the stroke. Using voxel-based morphometry on SPM12, we investigated differences in GM volume profiles between our two groups. Images were pre-processed using the automatic lesion identification (ALI) toolbox in order to delineate the lesion and ensure proper classification of brain tissues. Independent-sample t-tests were then performed to compare whole-brain GM volume in CTRLs vs. PSAs. Results: Compared to CTRLs, PSAs showed decreased GM volume in the right anterior cingulate cortex (ACC) and the left thalamus (p≤.05, FWE corrected for cluster size). Interestingly, PSAs also showed a trend towards increased GM volume as compared to CTRLs in the middle temporal gyrus (MTG) in the contralesional (i.e. right) hemisphere (p < .005, uncorrected). Conclusion: Our findings suggest that remote GM atrophy is present in the acute phase post-stroke in language-related regions among PSA patients. Both the thalamus and the ACC have been acknowledged to play an important role in language processing. The GM volume reduction of the thalamus could be due to the degeneration of the thalamocortical radiations. This could in turn explain the right ACC atrophy, given that thalamic nuclei project white matter fibers to this region. Our results also revealed that the right MTG, the contralesional homologue to a damaged language region, shows GM hypertrophy. This finding is consistent with two studies that found significantly increased GM volume in the exact same region in chronic PSA patients. It is also in line with functional neuroimaging studies that suggest a compensatory role for the right hemisphere in PSA. In conclusion, this study provides important insights into the structural reorganization of the language network in the acute phase post-stroke. Longitudinal studies are necessary to better explain these patterns of GM volume reduction and augmentation in relation to degenerative and compensatory mechanisms.

Topic Area: Language Disorders

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