Abstract TP18: Progressive White Matter Degeneration After Ischemic Stroke

Abstract

Background: White matter degeneration after ischemic stroke may herald post-stroke cognitive decline. FLAIR white matter hyperintensity (WMH) reflects tissue injury and accumulates around the infarct and in remote regions. But WMH volumetry is insensitive to regional or short-term progression. We compared WMH volumetry to a voxel-wise 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-ups were included. WMH lesion volumes were automatically segmented on serial FLAIR MRI. In the hemisphere contralateral to the infarct from 30 days onward, we compared longitudinal change in WMH volume to a voxel-wise regression of FLAIR signal change over time. We used T1 images as an intermediate to nonlinearly align serial FLAIR images to individual templates. 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 white matter and converted to a percentage of the intracranial volume. Results: 22 ischemic stroke patients (mean age 73 ± 8 years, NIHSS 4 ± 4, infarct volume 10.3 ± 23 cc) had on average 3 follow-ups over 343 days. In the non-stroke hemisphere, volumetry revealed lesion growth in 12. Mean lesion increase was 0.01 ± 0.20% per year. In voxel-wise analysis 15 patients had increasing FLAIR signal. Intensity increased in mean 0.11 ± 0.23% of intracranial voxels. Lesion growth was associated with the volume of voxel-wise signal increase (Beta = 0.51, p = 0.018). In the stroke hemisphere, progressive WMH expansion of peri-infarct tissue, consistent with Wallerian degeneration, was present in 10 patients. WMH regression, consistent with atrophy and infarct cavitation, was present in 14. Stroke hemisphere WMH expansion was associated with initial NIHSS (B = 0.58, p = 0.0086) while regression was associated with acute infarct volume (B = 0.80, p < 0.001). Conclusions: Voxel-wise longitudinal WMH analysis detects progressive white matter degradation and regional variation continuing 30 days after stroke.