High rebleeding risk associated with choroidal collateral vessels in hemorrhagic moyamoya disease: analysis of a nonsurgical cohort in the Japan Adult Moyamoya Trial

OBJECTIVE Choroidal collateral vessels typical of moyamoya disease have received attention as a potential bleeding source. The authors' previous angiographic cross-sectional analysis suggested a possible association between choroidal collaterals and posterior hemorrhage, indicating a high risk for rebleeding. The present longitudinal analysis is intended to determine whether choroidal collaterals are a predictor of rebleeding in hemorrhagic moyamoya disease. METHODS The Japan Adult Moyamoya Trial group designed an ancillary cohort study using 5-year follow-up data on 37 patients included in the nonsurgical arm of the original randomized controlled trial and compared the rebleeding rate of those with and those without choroidal collaterals, represented by the connection between the anterior or posterior choroidal arteries and the medullary arteries. An expert panel determined whether a choroidal collateral was present in each patient through the measurement of baseline angiography studies. The rebleeding rate comparison was adjusted for age, diagnosis of hypertension, and involvement of the posterior cerebral artery. RESULTS Choroidal collaterals were present in 21 patients (56.8%). The rebleeding rate was 13.1% per year in the collateral-positive group as compared with 1.3% in the negative group (p = 0.008, log-rank test). The adjusted hazard ratio for rebleeding in the collateral-positive group relative to the negative group remained statistically significant (HR 11.10, 95% CI 1.37-89.91). Radiographic assessment of the collateral-positive group revealed good correspondence between the distribution of collaterals and rebleeding sites. CONCLUSIONS Results of this study suggest that choroidal collaterals are a bleeding source with a high risk for hemorrhagic recurrence and a predictor of rebleeding in hemorrhagic moyamoya disease.