Abstract WP12: Evolution Of Regional Flair White Matter Hyperintensities After Ischemic Stroke: A Voxel-wise Approach

Abstract

Background: White matter (WM) degeneration after ischemic stroke may herald post-stroke cognitive decline. FLAIR WM hyperintensity (WMH) reflects tissue injury and accumulates around the infarct and in remote regions. But WMH volumetry is insensitive to regional progression. We compared WMH volumetry to a voxel-wise (VW) approach for detecting FLAIR WMH change longitudinally after stroke. Methods: Ischemic stroke patients enrolled in an observational cohort study underwent serial MRI acutely, at 1 month and every 3 months thereafter. Patients with 6 to 12-month follow-up were included. WMH lesion volumes were automatically segmented on serial FLAIR MRI. In the hemisphere contralateral to the infarct after 30 days, we compared longitudinal change in WMH volume to a VW regression of FLAIR signal change over time. Serial FLAIR images were nonlinearly aligned using a T1 intermediate. FLAIR intensities were normalized, corrected for local expansion/contraction, and smoothed. Within voxels identified as lesion at any timepoint, significant WMH change was determined relative to the normal appearing WM and converted to percent of total intracranial volume (TICV). Results: 22 stroke patients (mean age 73, NIHSS 4, infarct volume 10.3cc) had on average 3 follow-ups over 343 days. In the non-stroke hemisphere, volumetry revealed lesion growth in 12 participants (55%) while VW analysis revealed FLAIR signal increase in 15 (68%). For volumetry, mean lesion increase was 0.01 ± 0.20% of TICV per year while VW FLAIR intensity increased in mean 0.11 ± 0.23% of total intracranial voxels. Volumetric growth was associated with the volume of VW signal increase (Std Beta = 0.51, p = 0.02). In the stroke hemisphere, WMH expansion of peri-infarct tissue, consistent with Wallerian degeneration, was present in 10 participants (45%). WMH regression, consistent with atrophy or infarct cavitation, was present in 14 participants (64%). Stroke hemisphere WMH expansion was associated with higher NIHSS (Std B = 0.58, p = 0.009) while regression was associated with larger infarct volumes (Std B = 0.80, p < 0.001). Conclusions: In early chronic stroke, VW longitudinal WMH analysis detects progressive WM degradation with regional variation and may be more sensitive than gross volumetry.