Background: Extracranial-intracranial (EC-IC) bypass surgery is performed to reduce the risk of ipsilateral cerebral infarction in selected patients with chronic intracranial atherosclerotic steno-occlusive disease (ICAD) with reduced cerebral blood flow (CBF). However, postoperative watershed shift induced ischemic stroke (WSIS) may occasionally occur despite maintained bypass patency and improved CBF. We report the incidence and characteristic features of WSIS after superficial temporal artery-middle cerebral artery (STA-MCA) bypass for chronic WSIS.
Methods: We retrospectively analyzed 158 patients with symptomatic chronic ICAD and impaired CBF and cerebrovascular reactivity who underwent STA-MCA bypass between 2013 and 2023. Clinical data and pre- and postoperative imaging findings were analyzed to identify WSIS.
Results: Postoperative bypass patency was 100%. Ischemic complications occurred in 3 of 158 patients (1.9%), all of which were WSIS. Notably, 3 WSIS cases occurred in patients with severe internal carotid artery stenosis. These infarctions occurred on postoperative day 3, despite good bypass patency. Angiography confirmed bypass flow supplied the entire MCA, but anterograde ICA flow was consequently reduced, leading to a hemodynamic shift.
Conclusions: WSIS is a rare (1.9%), but important complication after STA-MCA bypass, occurring in patients who have preserved anterograde flow preoperatively.
Keywords: Atherosclerosis; Bypass; Infarction; Middle cerebral artery; Superficial temporal artery.
© 2025. The Author(s).