Performance of CT ASPECTS and collateral score in risk stratification: Can target perfusion profiles be predicted without perfusion imaging?

BACKGROUNDANDPURPOSE: Endovascular trials suggest that revascularization benefits a subset of acute ischemic stroke patients with large-Artery occlusion and small-core infarct volumes. The objective of our study was to identify thresholds of noncontrast CT-ASPECTS and collateral scores on CT angiography that best predict ischemic core volume thresholds quantified by CT perfusion among patients with acute ischemic stroke. MATERIALS AND METHODS: Fifty-four patients with acute ischemic stroke (<12 hours) and MCA/intracranial ICA occlusion underwent NCCT/CTP during their initial evaluation. CTP analysis was performed on a user-independent platform (RApid processing of PerfusIon and Diffusion), computing core infarct (defined as CBF of<30% normal). A target mismatch profile consisting of infarction core of≥50 mL was selected to define candidates with acute ischemic stroke likely to benefit from revascularization. RESULTS: NCCT-ASPECTS of <9 with a CTA collateral score of 3 had 100% specificity for identifying patients with a CBF core volume of <50 mL. NCCT-ASPECTS of ge;6 had 100% specificity for identifying patients with a CBF core volume of <50 mL. In our cohort, 44 (81%) patients had an NCCT-ASPECTS of ≤9, a CTA collateral score of 3, or an NCCT-ASPECTS of ≤6. CONCLUSIONS: Using an NCCT-ASPECTS of≤9 or a CTA collateral score of 3 best predicts CBF core volume infarct of<50 mL, while an NCCT-ASPECTS of ≤6 best predicts a CBF core volume infarct of <50 mL. Together these thresholds suggest that a specific population of patients with acute ischemic stroke not meeting such profiles may benefit most from CTP imaging to determine candidacy for revascularization.