Intraoperative immediately venous reddening indicates cerebral hyperperfusion after superficial temporal artery-middle cerebral artery anastomosis in moyamoya disease: illustrative case.

backgroundCerebral hyperperfusion (CHP) is a serious complication after bypass surgery in moyamoya disease (MMD). Currently, the prediction or diagnosis of CHP relies on various blood flow monitoring devices, and there is a lack of direct signs to predict the occurrence of CHP. OBSERVATIONS: The authors report on the case of a patient with MMD in whom the cortical veins were immediately reddened during superficial temporal artery (STA)-middle cerebral artery (MCA) bypass. On declamping the proximal STA during the operation, the blue vein near the anastomosis was rapidly arterialized under the microscope. Indocyanine green videography showed filling of the vein in the arterial phase, with a notable rise in venous blood flow, monitored by intraoperative laser speckle contrast imaging, and postoperative SPECT imaging demonstrated hyperperfusion in the territory of the MCA. LESSONS: The intraoperative venous reddening phenomenon indicated that the dramatic changes in venous blood flow may reflect CHP status after STA-MCA bypass surgery. https://thejns.org/doi/10.3171/CASE24600.