Contralateral stroke during carotid endarterectomy due to abnormalities in the circle of Willis.

Approximately 10-20% of patients will not tolerate cross-clamping of the common carotid artery for carotid endarterectomy procedures. The most frequent causes of neurological deficits are either embolization of particulate matter or cerebral hypoperfusion. Insufficient blood flow through primary collaterals of the circle of Willis is the main reason for hypoperfusion that requires immediate shunt placement. Although excessive preoperative imaging is not indicated in many patients undergoing disobliteration of a stenosed internal carotid artery, there are some patients with particular anatomic constellations who would benefit from a more detailed preoperative work-up. In these cases, the specific risk should be evaluated prior to surgery in order to make plans for appropriate intraoperative management regarding neurologic monitoring and shunt insertion. As regional anesthesia permits early detection of ischemic symptoms, it is advantageous in these patients. We report a case where regional anesthesia allowed early detection of rapidly progressing signs of bi-hemispheric brain ischemia in a patient with diabetes and with at that time unknown severe abnormalities of the circle of Willis. Lack of adequate collateralization was detected only after surgery, in a combined perfusion-magnetic resonance imaging study. In symptomatic diabetics with low-grade stenosis of the internal carotid artery, preoperative assessment of the function of the circle of Willis may therefore be helpful in predicting any increased risk for intraoperative cerebral ischemia.