Preoperative Evaluation of Circle of Willis Morphology in Patients Undergoing Carotid Endarterectomy

Cerebral ischemia during clamping of the carotid artery is a procedure-related complication in carotid endarterectomy (CEA). A correlation between the status of the circle of Willis, especially A1-A2 morphology, and the alteration of intraoperative somatosensory evoked potentials (SEP) was evaluated in 68 patients. All carotid endarterectomies were performed under general anesthesia without shunting. Patients were classified into 3 groups based on A1-A2 morphology in preoperative cerebral angiography. The amplitude of intraoperative SEP was decreased in 57.1% of patients with hypoplasia or absence of contralateral A1. On the other hand, amplitude was decreased in 26.7% of patients with hypoplasia or absence of ipsilateral A1 and in 11.4% of patients with patent bilateral A1. Incompleteness of the anterior part of the circle of Willis, especially hypoplasia or absence of contralateral A1, is a significant risk factor for developing of ischemia during clamping of the carotid artery.