Hyperintense ipsilateral cortical sulci on FLAIR imaging in carotid stenosis: ivy sign equivalent from enlarged leptomeningeal collaterals.

Fluid-attenuated inversion recovery (FLAIR) imaging provides high contrast between hyperintense lesions and normal tissue. Hyperintense structures in convexity sulci are commonly linked to abnormal cerebrospinal fluid composition, whether blood, protein, or infection. A patient with hemispheric transient ischemic attacks from severe carotid stenosis had hyperintense convexity sulci on FLAIR magnetic resonance imaging, interpreted as possible prior hemorrhage, making the patient ineligible for carotid stent reconstruction. Retrospective analysis revealed that hyperintense sulci were dilated leptomeningeal collaterals. In severe arterial disease causing cerebral hypoperfusion, dilated leptomeningeal vessels should be considered a cause for serpiginous hyperintense structures on FLAIR imaging, similar to the "ivy sign" described in moya-moya patients.