Hemorrhagic Stroke and the Japan Adult Moyamoya Trial

The Japan Adult Moyamoya (JAM) Trial was a unique randomized controlled trial demonstrating the effectiveness of direct bypass surgery for hemorrhagic moyamoya disease. Prespecified subgroup analysis undertaken as part of the trial demonstrated that posterior-dominant initial hemorrhage is a significant predictor of rebleeding and an effect modifier for surgery. Periventricular anastomosis—fragile collaterals formed by the lenticulostriate arteries, thalamic perforators, and choroidal arteries—might present a clue to the mechanism of high rebleeding risk linked to posterior hemorrhage. Angiographic analyses of the JAM Trial revealed that choroidal collaterals and the involvement of the posterior cerebral artery are associated with posterior hemorrhage, and subsequent cohort analysis of the nonsurgical group has revealed that choroidal anastomosis is a strong predictor of rebleeding. A better understanding of periventricular anastomosis might contribute to further progress in the surgical treatment of hemorrhagic moyamoya disease.