Staged bilateral superficial temporal artery-middle cerebral artery bypass with collateral preservation in advanced moyamoya disease: A technical case report

Background: In advanced moyamoya disease (MMD), cerebral perfusion may depend on transdural collaterals from external carotid artery branches. Direct revascularization can provide immediate flow augmentation, but surgical bypass can jeopardize those same compensatory vessels. We describe stage two of a bilateral direct bypass in a patient with recurrent ischemic strokes, focusing on collateral-aware perioperative planning, intraoperative neuroprotection, and graft-flow verification. Case Description: We report a patient in her late fifties with bilateral MMD and multiple prior strokes who underwent staged bilateral superficial temporal artery (STA) to middle cerebral artery (MCA) bypass. Eight days after contralateral revascularization, a left-sided bypass was performed. Intraoperative navigation identified hypertrophied middle meningeal artery (MMA) branches collateralizing to the anterior cerebral artery (ACA), which were preserved to maintain perfusion to the ACA territory. Neuroprotective measures were deployed including papaverine, heparinized saline flush, mild hypothermia, and thiopentone to reduce ischemia during temporary MCA clipping. Controlled hypertension was induced to further enhance collateral flow. Patency was confirmed with Doppler ultrasonography and indocyanine green angiography, and postoperative imaging several months after the second stage confirmed bilateral bypass patency with no new infarction. Conclusion: The educational value of this case lies in distinguishing the STA donor from the MMA collateral pathway and tailoring the bone opening to protect the latter. It demonstrates how staged revascularization, meticulous collateral preservation, targeted intraoperative neuroprotection, and multimodal verification of graft flow can be integrated in the management of complex bilateral MMD and provides practical technical and perioperative lessons for cerebrovascular surgeons undertaking direct bypass in patients with critically flow-dependent collateral circulation.