Abstract TMP71: Hypoperfusion And Thromboembolism Are Codominant Stroke Mechanisms In Adult Moyamoya Disease

Background: Treatment of moyamoya disease (MMD) has predominantly focused on flow augmentation since the mechanism of ischemic stroke has largely been attributed to hemodynamic failure. Recent studies have challenged this notion suggesting that thromboembolism may play a dominant role. The aim of our study was to investigate the mechanisms of ischemic stroke in MMD by assessing the relationship between infarction patterns and Quantitative Magnetic Resonance Angiography (QMRA) flow state. Methods and Results: This is a retrospective study of adult patients with suspected MMD that presented with MRI confirmed acute ischemic stroke predating or following QMRA by a maximum of six months, between 2009 and 2021. Of the 177 consecutive patients with MMD that underwent QMRA, 35 patients met inclusion, consisting of 41 hemispheres. Flow-status was dichotomized into low-flow and normal-flow based on published criteria. Mixed pattern was the most frequent finding (70.7%), followed by embolic (17.1%), perforator (7.3%), and internal borderzone (IBZ) (4.9%). Infarction patterns were then dichotomized into IBZ+ (internal borderzone alone or mixed) and IBZ- (no internal borderzone constituent) based on the constituents of the patterns. Low-flow states were insignificantly more frequent with IBZ+ compared to IBZ- (48.4% vs. 20.0%, p = 0.14). Ipsilateral PCA fractional flow was significantly higher with IBZ+ compared to IBZ- (345.0% vs. 214.7%, p = 0.04). Conclusions: Mixed infarction pattern was the most common pattern of infarction in patients with MMD, implying that at least 2 interrelated stroke mechanisms of hypoperfusion and thromboembolism likely coincide. An association between ICA flow status and the pattern of infarction was not found. Prospective studies evaluating the utility of antithrombotic agents in MMD are needed.