FLAIR Vascular Hyperintensities in Acute ICA and MCA Infarction: A Marker for Mismatch and Stroke Severity?

Background: Vascular hyperintensities of brain-supplying arteries on stroke FLAIR MRI are common and represent slow flow or stasis. FLAIR vascular hyperintensities (FVH) are discussed as an independent marker for cerebral hypoperfusion, but the impact on infarct size and clinical outcome in acute stroke patients is controversial. This study evaluates the association of FVH with infarct morphology, clinical stroke severity and infarct growth in patients with symptomatic internal carotid artery (ICA) or middle cerebral artery (MCA) occlusion. Methods: MR images of 84 patients [median age 73 years (IQR 65–80), 56.0% male, median NIHSS 7 (IQR 3–13)] with acute stroke due to symptomatic ICA or MCA occlusion or stenosis were reviewed. Vessel occlusions were identified by MRA time of flight and graded with the TIMI score. Diffusion and perfusion deficit volumes on admission and FLAIR lesion volumes on discharge were assessed. The presence and number of FVH were evaluated according to MCA-ASPECT areas, and associations with MR volumes, morphology of infarction, recanalization status, presence of white matter disease and hemorrhagical transformation as well as with stroke severity (NIHSS), stroke etiology and thrombolysis rate were analyzed. Results: FVH were detectable in 75 (89.3%) patients. The median number of FVH was 4 (IQR 2–7). Patients with FVH >4 presented with more severe strokes due to NIHSS (p = 0.021), had larger initial DWI lesions (p = 0.008), perfusion deficits (p = 0.001) and mismatch volumes/ratios (p = 0.005). The final infarct volume was larger (p = 0.005), and hemorrhagic transformation was more frequent (p = 0.029) in these patients. Conclusions: The presence of FVH indicates larger ischemic areas in brain parenchyma predominantly caused by proximal anterior circulation vessel occlusion. A high count of FVH might be a further surrogate marker for initial ischemic mismatch and stroke severity.