Hyperintense vascular sign on MRI for evaluating cerebrovascular disease: methods, features, and clinical significance.

The hyperintense vessel sign (HVS) on magnetic resonance imaging is a recognized surrogate marker of cerebral hemodynamic impairment, presumed to reflect slow-flowing collateral blood distal to arterial stenosis or occlusion. This narrative review critically synthesizes the literature on HVS across T2 fluid-attenuated inversion recovery (FLAIR), arterial spin labeling (ASL), contrast-enhanced T1-weighted imaging, and high-resolution vessel wall imaging (HR-VWI). On FLAIR, the FLAIR vascular hyperintensity sign provides evidence for noninvasive assessment of ischemia risk, disease progression, and clinical prognosis. On ASL, arterial transit artifacts indicate collateral recruitment and delayed arterial transit time. On HR-VWI, the intravascular enhancement sign offers complementary hemodynamic information alongside vascular wall assessment. Conventional enhanced T1WI is mainly applicable in Moyamoya disease assessment. Despite consistent evidence linking HVS to collateral recruitment, discrepancies regarding prognostic value persist across studies due to methodological heterogeneity. We propose a practical, sequence-specific provisional conceptual framework that incorporates ASPECTS-based FLAIR grading, multi-delay ASL protocols, and HR-VWI vessel counts to standardize assessment and facilitate cross-study comparability. Future priorities include longitudinal HVS monitoring, validated grading thresholds, and multi-modal quantitative tools.