Objective: Choroidal anastomosis (ChA) has been implicated as the main indicator of an increased hemorrhagic risk in adult moyamoya disease. In this retrospective study, the authors aimed to identify the potential risk factors that can influence the rupture of ChA. Methods: The authors evaluated the clinical and radiological data on brain hemispheres positive for ChA from September 2019 to March 2023. The rupture status of the ChA was determined using previously described methods. Two independent raters quantitatively investigated the lumen diameter (LD) and lumen area (LA) of the ChA using high-resolution vessel wall imaging (VWI). Multivariate logistic regression analysis was conducted to identify the risk factors for ruptured ChA. Results: Ruptured and unruptured ChAs were identified in 16 and 60 hemispheres, respectively. Univariate analysis showed that the mean values of the LD (1.251 +/- 0.241 vs 0.967 +/- 0.214 mm, p < 0.001) and LA (1.607 +/- 0.445 vs 0.945 +/- 0.372 mm2, p < 0.001) of ChAs were significantly greater in the ruptured group than in the unruptured group. A periventricular anastomosis (PA) score of 1, indicating the angiographic presence of ChA alone, was more prevalent in the ruptured group than in the unruptured group (43.8% vs 11.7%, p = 0.003). Multivariate analysis demonstrated that a larger LA of the ChA (OR 37.01, 95% CI 5.787-236.7, p < 0.001) and PA score 1 (OR 6.661, 95% CI 1.260-35.21, p = 0.026) were independently associated with ruptured ChA hemispheres. Receiver operating characteristic curve analysis revealed that the optimal cutoff point for the LA was 1.285 mm2 (sensitivity 81.3%, specificity 86.7%). Conclusions: A larger LA (> 1.285 mm2) of the ChA and the angiographic presence of ChA alone are independent risk factors for a ruptured ChA. Revascularization surgery for the prevention of future hemorrhage may be indicated for hemispheres with a high-risk unruptured ChA. These characteristics may help to determine treatment strategies for patients with an unruptured ChA.
