Perfusion-Weighted Magnetic Resonance Imaging Is A Poor Indicator Of Hemodynamic Compromise In Vertebrobasilar Disease

Introduction: Perfusion-weighted magnetic resonance imaging (MRP) has been used to assess changes in cerebral perfusion attributable to vascular stenosis or occlusion that may predict stroke risk. The ability of MRP to identify hemodynamic compromise in the posterior circulation, however, has not been well established. The observational Vertebrobasilar Flow Evaluation and Risk of Transient Ischemic Attack and Stroke (VERiTAS) study has previously demonstrated that flow status determined through large vessel flow measurements with quantitative magnetic resonance angiography (QMRA) predicts stroke risk in vertebrobasilar disease. We examined whether MRP parameters correlated with QMRA assessment of flow compromise in the VERiTAS cohort. Methods: VERiTAS enrolled patients with recent vertebrobasilar transient ischemic attack or stroke and ≥50% atherosclerotic stenosis or occlusion in vertebral and/or basilar arteries. Hemodynamic status using vertebrobasilar large vessel flow was measured using QMRA, and patients were designated as low or normal flow based on distal territory regional flow, incorporating collateral capacity. Dynamic susceptibility contrast MRP was performed concurrently with QMRA. Mean transit time (MTT) in the posterior cerebral artery (PCA) territory was used to evaluate posterior circulation perfusion. To normalize the values, an MTT ratio was calculated in reference to the anterior circulation (mean of the anterior cerebral artery (ACA) and middle cerebral artery (MCA) territories). The PCA to ACA/MCA MTT ratio from MRP was then assessed relative to flow status (normal vs. low) from QMRA. Results: Of the 72 enrolled subjects, 23 had MRP data available for review. On initial QMRA designation, 19 subjects were designated as normal flow vs. 4 as low flow. The mean MTT ratios for patients with normal vs. low flow were 1.02 (SD=0.05) vs.1.04 (SD=0.04), respectively (p=0.55, t test; p=0.50, Wilcoxon rank sum test). Among the subgroup of 23 patients, 1 patient with low flow, and MTT ratio of 1.00, experienced a recurrent stroke. Conclusions: These results suggest that MRP is a poor indicator of actual hemodynamic compromise in vertebrobasilar disease and is not a reliable substitute for large vessel flow measurements.