Abstract WMP18: Regional Comparison of Functional Connectivity Between “Salvaged” Peri-Infarct and Infarcted Tissue

Abstract

Introduction: Even when accounting for lesion topography, radiological Final Infarct Volume (FIV) after acute ischemic stroke (AIS) correlates only moderately with clinical outcome. Pathology in normal-appearing “salvaged” peri-infarct tissue and partial preservation within radiologically infarcted tissue may contribute to the variance between FIV and clinical outcome. We sought to evaluate the degree of neuronal dysfunction within infarcted, peri-infarct and remote regions on follow-up MRI after AIS. Methods: In a single-centre prospective study, twenty AIS patients underwent resting state functional MRI at 1 month. Asymmetry compared to the contralateral hemisphere in connectivity values (CV) was compared between 4 Regions of Interest (ROIs) defined on admission CT perfusion and 1-month MRI: (1) Early Ischemic Core with severe oligemia at presentation (>10s Tmax on admission CTP and FLAIR positivity); (2) Evolved Infarct with mild-moderate oligemia at presentation (4-8s Tmax on CTP and FLAIR positivity); (3) Peri-infarct “salvaged penumbral” tissue (>6s Tmax on CTP and FLAIR negativity); (4) remote non-ischemic tissue (normal CTP and FLAIR). Results: Asymmetry in CV were significantly different between all ROIs (p=0.018) in a preliminary analysis (n=9). Early Infarct and Evolved Infarct both showed dysfunction when compared to the contralateral hemisphere (CV = 0.384 & 0.247 respectively, p=0.717). Peri-Infarct Tissue had more dysfunction than remote tissue (CV = 0.427 vs 0.838, p=0.03) despite both being normally-appearing. Overall, Asymmetry in CV was greatest in Infarcted tissue followed by Peri-infarct Tissue and Remote Tissue. Conclusion: Peri-infarct tissue demonstrates dysfunction despite being radiologically normal. Our data suggest a gradient of neuronal injury extending beyond conventionally-delineated infarct boundaries is present in the chronic post-stroke phase.