Persistent Periventricular Anastomosis Associated With Rebleeding After Bypass Surgery for Hemorrhagic Moyamoya Disease.

Background: Although bypass surgery can reduce rebleeding risk in hemorrhagic moyamoya disease, the risk remaining after surgery is not negligible. We hypothesized that the postoperative persistence of periventricular anastomosis (PA), a fragile periventricular collateral manifestation, is associated with rebleeding. Methods: This retrospective cohort study included patients with moyamoya disease who underwent direct bypass at 2 institutions after hemorrhagic presentation. Either presence or absence of PA after surgery was radiologically determined by grading of each subtype, lenticulostriate, thalamic, or choroidal anastomosis, 3-6 months after surgery. The time interval between the surgery and the rebleeding event or last visit was calculated. Results: Of 116 eligible patients comprising 232 hemispheres, 172 hemispheres underwent surgery. Rebleeding occurred in 16 hemispheres of 15 patients (2.0% per person-year) during the median follow-up period of 6.3 years. The hemisphere-based annual rebleeding rate was 2.0% in the PA-positive hemispheres as compared with 0.46% in the PA-negative hemispheres. The adjusted hazard ratio of rebleeding for positive PA relative to negative PA was 4.11 (95% CI, 1.07-15.82). Among subtypes of PA, lenticulostriate anastomosis was the most likely to persist after surgery (34 of 62 anastomoses) and to cause rebleeding (8 of 16 hemispheres). Conclusion: The persistence of PA, especially that of lenticulostriate anastomosis, might be associated with rebleeding after surgery. This suggests the importance of assessing and optimally managing PA for improving long-term outcomes.