Hemorrhage and risk of further hemorrhagic strokes following cerebral revascularization in Moyamoya disease: A review of the literature

BACKGROUND: We sought to review the current literature with regards to future risks of hemorrhage following cerebral revascularization in Moyamoya disease (MMD). METHODS: We performed a comprehensive literature review using PubMed to inspect the available data on the risk of hemorrhage after revascularization in MMD. RESULTS: In this review, we identify the risk factors associated with hemorrhage in MMD both before and after cerebral revascularization. We included proposed pathophysiology of the hemorrhagic risk, role of the type of bypass performed, treatment options, and future needs for investigation. CONCLUSIONS: The published cases and series of MMD treatment do show a risk of hemorrhage after treatment with either direct or indirect bypass both in the immediate as well as long-term future. While there are no discernible patterns in the rate of these hemorrhages, there is Class III evidence for the predictive effect of multiple microbleeds on preoperative imaging. Also, whereas revascularization, both direct and indirect, has been shown to reduce ischemic complications from MMD, there is not an association with the risk of hemorrhage after the procedure. Further studies need to be performed to help evaluate what the risk factors are and how to counsel patients as to the long-term outlook of this disease process.