Relationship Between Circle of Willis Morphology on 3D Time-of-Flight MR Angiograms and Transient Ischemia During Vascular Clamping of the Internal Carotid Artery During Carotid Endarterectomy

BACKGROUND AND PURPOSE: A potential source of complication at carotid endarterec-tomy (CEA) is cerebral ischemia caused by hypoperfusion during clamping of the carotid artery. Configuration of primary collateral pathways may be a major risk factor for develop-ment of transient cerebral ischemia during clamping. We investigated whether circle of Willis morphology on 3D time-of-flight (TOF) MR angiograms can reliably predict transient ischemia during vascular clamping of the internal carotid artery (ICA) in patients undergoing CEA. METHODS: Three-dimensional TOF MR angiography and CEA were performed in 117 patients. Patients had unilateral stenosis (n 86), unilateral stenosis with contralateral occlusion (n 21), or bilateral severe stenosis (n 10) of the ICA. Circle of Willis morphology on preoperative 3D TOF MR angiograms was analyzed and correlated with intraoperative history of ischemia during vascular clamping of the ICA. RESULTS: Patients with unilateral stenosis or bilateral severe stenosis experienced transient ischemia during clamping of ICA at a low rate (11 [11%] of 96). In these groups, we found no specific circle of Willis patterns associated with development of intraoperative ischemia. However, patients with contralateral ICA occlusion experienced ischemia frequently during