Postoperative posterior MCA territory infarction following single-barrel STA-MCA bypass with hemodynamic territory mismatch in moyamoya disease: A case report.

The success of superficial temporal artery-to-middle cerebral artery (STA-MCA) bypass in moyamoya disease (MMD) depends not only on anastomotic patency but on whether the revascularized territory corresponds to the most hemodynamically compromised region. We report a case of postoperative posterior MCA territorial infarction attributable to hemodynamic territory mismatch. A 47-year-old woman with bilateral MMD presented with progressive left hemiparesis. Preoperative computed tomography (CT) perfusion demonstrated markedly reduced cerebral blood flow (CBF) and diffuse mean transit time (MTT) prolongation, most pronounced in the right posterior MCA and posterior cerebral artery (PCA) territory. Digital subtraction angiography (DSA) identified prominent choroidal periventricular anastomosis (ChA-PA) as a marker of deep perforator territory hemodynamic stress. She underwent right single-barrel STA-MCA bypass using the frontal STA branch anastomosed to a temporal M4 branch, combined with encephalo-duro-arterio-synangiosis (EDAS). Despite confirmed patency on intraoperative indocyanine green (ICG) videoangiography, she developed acute infarction in the right posterior MCA territory on postoperative day 1 - the region not covered by the temporal anastomosis. Two-month follow-up DSA demonstrated bypass patency and regression of ChA-PA. This case highlights the importance of preoperative perfusion-guided bypass planning to avoid hemodynamic territory mismatch. In patients with posterior MCA territory compromise, anastomosis should target the most ischemic region, or double-barrel bypass should be considered.