Abnormal collateral channels, so-called moyamoya vessels, play a critical role to compensate cerebral ischemia, but carry the risk for hemorrhagic stroke in moyamoya disease (MMD). The present study was aimed to clarify if superficial temporal artery to middle cerebral artery (STA-MCA) anastomosis and encephalo-myo-duro-arterio-pericranial synangiosis (EDMAPS) can efficiently regress the abnormal collateral channels in MMD patients.
This study included 92 hemispheres of 61 MMD patients who underwent STA-MCA anastomosis combined with EDMAPS between 2013 and 2019. There were 17 children and 44 adults. We retrospectively analyzed the findings on cerebral angiography before and 3 to 6 months after surgery, including Suzuki’s angiographical stage, the development of surgical collaterals, and the extent of abnormal collateral channels such as lenticulostriate, thalamic, and choroidal channels.
Following surgery, no pediatric and adult patients experienced any stroke during follow-up periods (40.2±25.5 and 54.9±19.7 months, respectively). Suzuki’s stage significantly advanced in both adult and pediatric patients after surgery (P=0.042 and P<0.001). In adult patients, all of the lenticulostriate, thalamic, and choroidal channels significantly regressed after surgery (P<0.001, P=0.012, and P=0.004, respectively). In pediatric patients, however, lenticulostriate and choroidal channels significantly regressed (P=0.005 and P=0.034, respectively). Correlation analysis revealed that the development of surgical collaterals determined the postoperative regression of choroidal channels (P<0.001).
STA-MCA anastomosis and EDMAPS may be one of the most effective procedures to widely provide surgical collaterals to the operated hemispheres and prevent not only ischemic but also hemorrhagic stroke by regressing the hemorrhage-prone abnormal collateral channels in MMD.

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