Vascular hyperintensities on baseline FLAIR images are associated with functional outcome in stroke patients with successful recanalization after mechanical thrombectomy

•The degree of collateral circulation is a critical prognostic factor in patients with acute ischemic stroke because it promotes a higher rate of effective recanalization.•The prognostic value of vascular hyperintensities on fluid-attenuated inversion recovery (FLAIR) MR images in patients achieving effective recanalization after mechanical thrombectomy is not well known.•Poorly extended vascular hyperintensities on FLAIR images at admission MRI are associated with a poor functional outcome at three months despite successful recanalization using mechanical thrombectomy.