Purpose: Hyperintense vessels (HVs) on fluid-attenuated inversion recovery (FLAIR) imaging are associated with the leptomeningeal collateral circulation in cases of arterial occlusive lesions. Nevertheless, the relationship between HVs on FLAIR imaging and arterial circulation time (ACT) on cerebral angiography has not been defined.
Methods: We analyzed images of 11 patients with acute occlusion of the distal internal carotid artery or proximal middle cerebral artery and calculated the difference in ACT (DACT) between infarcted and normal hemispheres. ACT was defined as the time interval from the initial opacification of the ipsilateral or contralateral cavernous internal carotid artery to the late arterial phase of the carotid artery territories. We scored HVs on FLAIR imaging using a modified Alberta Stroke Program Early Computerized Tomography Score (ASPECTS) and determined collateral circulation by grading collateral flow.
Results: We detected HVs on FLAIR images in 10 patients (median score, 4; range, 0 to 6). Comparison of infarcted and normal hemispheres demonstrated absent or subtle HVs on FLAIR imaging when the DACT was too short (<one second) or too long (>7.98 s) and prominent HVs with moderate DACT (2 to 5 s). The score of HVs on FLAIR was estimated well by DACT using a quadratic regression model (R(2) = 0.602) and better than by grading collateral flow (R(2) = 0.256).
Conclusion: In cases of large arterial occlusion, the hyperintensity of vessels on FLAIR images may be dependent on arterial circulation time via retrograde filling of the leptomeningeal collateral circulation.