405 The Impact of Cerebral Revascularization on Pial Collateral Flow in Patients With Moyamoya Disease Using Quantitative Magnetic Resonance Angiography

INTRODUCTION: Moyamoya disease (MMD) is a chronic steno-occlusive disease primarily of the anterior circulation leading to significant pial collateralization. Changes in the distribution of intracranial blood flow after revascularization surgery are not well understood. METHODS: We conducted a retrospective chart review of 46 patients with unilateral MMD who underwent cerebral revascularization from 2011-2019. Patients who underwent pre- and post- QMRA NOVA were included in the study. Flow was measured at the M1 segment of the middle cerebral artery (MCA), P2 segment of the posterior cerebral artery (PCA), and A2 segment of the anterior cerebral artery (ACA). Pial collaterals were defined as the sum of (A2+P2) flow. Total hemispheric flow was calculated as (M1+PCA+A2) pre-operatively and (M1+PCA+A2+Bypass) post-operatively, with the incorporation of the bypass graft. RESULTS: A total of 46 patients with unilateral MMD underwent revascularization with pre and post QMRA. Total intracranial flow at baseline prior to revascularization was lower in the side of disease (214.9 ml/min vs. 269.1 ml/min). Total intracranial flow at baseline after revascularization remained lower on the ipsilateral side of disease with an increased flow in the contralateral healthy side (211.7 ml/min vs 286.1 ml/min). Pre-bypass there was a higher flow through pial collaterals on the ipsilateral diseased side (183 ml/min) than the contralateral healthy side (135 ml/min). Post-bypass this difference in pial flow between ipsilateral and contralateral sides decreased from 48 ml/min to 22 ml/min (p = 0.02). Collateral ratio decreased significantly (0.46 preoperatively vs. 0.18 postoperatively) (P < 0.01). CONCLUSIONS: The results of this study quantitatively confirm that direct cerebral revascularization decreases collateral stress in patients with moyamoya disease.