FLAIR Vascular Hyperintensities Indicate Slow Poststenotic Blood Flow in ICA Stenosis

Purpose Occlusion or significant stenosis of the internal carotid artery (ICA) in the cervical segment is commonly associated with a poststenotic decrease in the downstream blood flow and perfusion. Fluid attenuated inversion recovery (FLAIR) vascular hyperintensities (FVH) are a phenomenon that represents slow arterial blood flow. In this study, we investigated the frequency and extent of FVH in the distal ICA in patients with proximal ICA stenosis. Methods We analyzed the magnetic resonance imaging (MRI) findings in 51 patients with a total of 60 cervical ICA stenoses with special focus on the frequency and extent of FVH in the area of the petrous segment of the ICA on FLAIR images and correlated these with Doppler/duplex sonography results. Results In 46 (76.7%) patients with ICA stenosis, FVH could be detected in the petrous segment of the ICA: in 19 (41.3%) patients a thin hyperintense rim near the vessel wall (grade 1), in 24 (52.2%) patients a strong hyperintense rim near the vessel wall (grade 2), and in 3 (6.5%) patients a hyperintense filling of the entire lumen (grade 3) was observed. The extent of FVH in the ICA in the petrous segment showed a high negative correlation with the poststenotic flow velocity (Spearman correlation, R = –0.75, p < 0.001), and moderate correlation with the degree of ICA stenosis (Spearman correlation, R = 0.51, p < 0.001). Conclusion An FVH in the petrous ICA is commonly seen among patients with steno-occlusive disease in proximal ICA and could therefore be useful to recognize a proximal ICA stenosis even on FLAIR images.