Author Affiliations: Department of Neurology, University of Southern California, Los Angeles (Dr Sanossian); and the Stroke Center and Department of Neurology, University of California, Los Angeles (Drs Hao and Liebeskind).
A frequently encountered imaging finding in acute ischemic stroke and other cerebrovascular diseases is high-signal intensity within blood vessels on fluid-attenuated inversion recovery (FLAIR) magnetic resonance imaging sequences. Vascular hyperintensity (FVH) in FLAIR has been associated with large-vessel occlusion or stenosis.1 As opposed to other vessel signs seen in arterial insufficiency, FVH is unique in that it does not represent the thrombus, but rather is a representation of the sluggish or disordered blood flow through vessels, most often leptomeningeal collaterals.2,3 Normally in FLAIR, blood vessels have a loss of signal intensity owing to the “flow void” phenomenon in which blood protons move out of imaging section before the section-selective 180° pulse is applied, so that a spin-echo is not formed; FVH represents the relative absence of this flow void.4
Sanossian N, Hao Q, Liebeskind DS. The Thrombus and Discontinuity of FLAIR Vascular Hyperintensity. Arch Neurol. 2011;68(7):950-951. doi:10.1001/archneurol.2011.143