A novel system for evaluating collateralization of the external carotid artery after cerebral revascularization in moyamoya disease

OBJECTIVE The objective of this retrospective study was to establish a novel system for evaluating collateralization of the external carotid artery in patients with moyamoya disease (MMD) following direct and indirect revascularization surgeries. METHODS The authors conducted a retrospective analysis of 456 patients diagnosed with MMD who underwent direct and indirect revascularization procedures at Beijing Tiantan Hospital, Capital Medical University, between January 2015 and May 2023. Using a newly proposed digital subtraction angiography (DSA)–based evaluation system, the authors assessed collateralization angiogenesis objectively and in a standardized manner. RESULTS The authors’ findings indicated that there was no significant difference in collateralization angiogenesis between patients undergoing direct or indirect cerebral revascularization (p = 0.702). However, after cerebral revascularization, patients with ischemic MMD exhibited significantly higher collateralization angiogenesis compared with those with hemorrhagic MMD (p = 0.007). Children with MMD demonstrated higher angiogenesis levels than adults (p < 0.001), but subgroup analysis showed age-specific variations. In adults, collateralization angiogenesis was significantly greater in those with ischemic MMD (p = 0.006), whereas in children, no significant difference was noted between ischemic and hemorrhagic MMD (p = 0.962). Furthermore, regardless of MMD type, direct and indirect revascularization methods yielded similar collateralization angiogenesis (p = 0.962 and p = 0.963, respectively). Importantly, the Matsushima grading system revealed significant differences in angiogenesis in patients with ischemic MMD (p < 0.001). CONCLUSIONS The newly introduced DSA-based evaluation system offers an objective and standardized method for assessing collateralization angiogenesis in MMD. This study supports the efficacy of both direct and indirect revascularization surgical procedures and highlights distinct pathophysiological processes of ischemic and hemorrhagic disease subtypes. These findings contribute to a better understanding of surgical outcomes and aid in the selection of appropriate treatment strategies for patients with MMD.