Abstract 1905: Arterial Spin-Labeled MRI of Leptomeningeal Collateral Perfusion in Acute Ischemic Stroke

Abstract

Background: Leptomeningeal collaterals and associated cortical perfusion downstream from a proximal arterial occlusion or stenosis are potent predictors of outcome in acute stroke. Arterial spin-labeled (ASL) MRI may depict delayed arterial transit effects (DATE) of these collaterals and cerebral blood flow (CBF), utilizing noninvasive techniques without the use of contrast. We conducted a prospective validation study of ASL DATE and CBF as biomarkers of leptomeningeal collateral perfusion compared to digital subtraction angiography (DSA) and dynamic susceptibility contrast (DSC) perfusion MRI in acute ischemic stroke. Methods: Consecutive anterior circulation acute ischemic stroke patients admitted during a 1-year period were evaluated with pseudo-continuous ASL, DSA and DSC perfusion MRI within 12 hours of symptom onset. ASL DATE extent was scored using a 3-point scale and angiographic collaterals on the DSA graded using the ASITN/SIR collateral score. ASL CBF and DSC CBF maps were co-registered to derive comparative ROI statistics on perfusion in the symptomatic territory. ASL CBF lesions < 15 mL/100 g/min were used to measure DSC CBF values within coregistered ROIs. Results: Among 39 patients meeting entry criteria, mean age was 66±19 years and 51% were male. All 39 patients were imaged with ASL and DSA, with DSC perfusion MRI in a subset of 27. Sites of vascular occlusion or stenosis were: terminal ICA - 10, M1 MCA - 20, M2 MCA - 5 and more distal MCA - 4. ASL DATE scores ranged from 0-2, with a median of 1. DSA collateral grade ranged from 0-4, with a median of 2. Overall, there was strong correlation (r=0.702, p<0.001) between the ASL and DSA measures of leptomeningeal collateral supply. In the downstream territory from these leptomeningeal collaterals, ASL CBF and DSC CBF maps both revealed hypoperfusion in regions that closely matched. Only limited correlation, however, was noted between exact ASL CBF and DSC CBF values within the co-registered ROIs. Conclusions: ASL MRI provides an accurate, noninvasive measure of leptomeningeal collateral perfusion in acute ischemic stroke due to anterior circulation stenosis or occlusion. ASL CBF measures of collateral perfusion likely are arterially weighted, like DSA collateral grades, and unlike conventional DSC perfusion MRI CBF values.