Abstract 177: Hemodynamics and Anatomic Evaluation of Intracranial Arteriovenous Malformations Using Phase-Contrast Magnetic Resonance Velocimetry

Abstract

Introduction: Arteriovenous Malformations (AVMs) have a high lifetime risk of hemorrhage; however treatment carries a significant risk of morbidity/mortality. Wall Shear Stress (WSS) and other hemodynamic parameters are shown to be altered in patients with symptomatic AVMs. Analysis of hemodynamics may have value in stratifying patients into different risk groups to prioritize treatment. We have recently implemented PC-VIPR, a phase contrast MRA technique that can acquire whole brain angiograms with scan time of 5 minutes with velocity data. PC-VIPR has sufficient spatial resolution for both hemodynamic analysis and assessment of anatomic features such as Spetzler-Martin grading. Materials & Methods: 10 patients with AVMs were scanned using PC-VIPR; WSS and vessel diameter in vessels feeding the AVMs and in normal contralateral vessels were calculated using PC-VIPR velocity data using automated B-spline interpolation. Spetzler-Martin grading was performed by an experienced neuroradiologist. Results: Patients with an asymptomatic presentation or mild symptoms (n=4) had no significant difference in WSS between ipsilateral feeding vessels and normal contralateral vessels (1.555 N/m2 vs 1.494, p=0.31), and showed significant vessel dilation in feeding vessels when compared to normal contralateral vessels (4.57 mm vs 3.66, p=0.005) while patients presenting with hemorrhage, severe headaches/seizures, or focal neurologic deficits (n=6) had significantly higher WSS in feeders compared to contralateral vessels (1.607 N/m2 vs 1.146, p=0.003) but the increase in vessel dilation was not statistically significant. (4.34 vs 3.84, p=0.11) Spetzler-Martin grading was performed in all patients and correlated with grading performed via digital subtraction angiography in all cases. Discussion: In this study we demonstrate that both hemodynamic analysis and Spetzler-Martin grading can be obtained non-invasively in patients with AVMs using PC-VIPR. Variation in WSS between feeders and normal vessels appeared to relate to the clinical presentation of the patient. Figure 1a shows a WSS map of a patient with mild stable symptoms demonstrating similar WSS in feeders compared to contralateral vessels, Figure 1b shows a WSS map of a patient presenting with hemorrhage with higher WSS in feeders compared to contralateral vessels. Several reports suggest high WSS in AVM feeders stimulates compensatory dilation, normalizing WSS. Hemodynamic analysis using PC-VIPR may have value in risk stratification by identifying patients in which compensation has not yet occurred, with increased risk of hemorrhage.