Association of retrograde bypass flow depth along cortical recipient arteries with revascularization outcomes in direct bypass surgery for Moyamoya disease

Objective: During the cerebral digital subtraction angiography (DSA) follow-up after direct bypass surgery in patients with Moyamoya disease (MMD), we observed different depths of retrograde bypass flow along the original middle cerebral artery (MCA) pathway into the intracranial cavity through the anastomosed recipient vessels. The aim of this study was to investigate the relationship between these varying depths of retrograde bypass flow and the outcomes of revascularization. Methods: We conducted a retrospective study that included 109 patients (138 hemispheres) diagnosed with MMD and who underwent direct bypass surgery with subsequent DSA follow-up from 2022 to 2023. The study involved categorizing the retrograde flow of blood from superficial temporal artery (STA) into different segments of middle cerebral artery (MCA) as Retrograde Flow Level 1, Retrograde Flow Level 2, and Retrograde Flow Level 3, and correlating these definitions with the Matsushima grading system. We further investigated the correlation between the depth of retrograde bypass flow and fundamental patient characteristics, including sex, age, underlying medical conditions, side of surgery, preoperative diameter of the donor vessel STA, postoperative cerebral hemorrhage or infarction, and compensatory status of the middle meningeal artery and ophthalmic artery preoperatively. Results: Different retrograde flow levels were correlated with the Matsushima grading (P<0.001), and preoperative diameter of the donor vessel STA was significantly larger in the Retrograde Flow Level 3 group compared to the Retrograde Flow Level 2 group. Conclusions: The depth of retrograde flow in the recipient vessel MCA after direct bypass surgery for MMD was positively correlated with the Matsushima grading, which may serve as a novel method for evaluating the effectiveness of postoperative revascularization.