Some variations of the circle of Willis, important for cerebral protection in aortic surgery - a study in Eastern Europeans

Background: During unilateral selective cerebral perfusion (SCP), via canulation of the brachiocephalic trunk, the brain receives blood only through the right common carotid artery and the right vertebral artery. For perfusion of the contralateral (left) hemisphere it is counted on the competence of the circle of Willis (Cow). It is well known that variations of Cow are present in more than 50% of the people. Furthermore, these variations usually affect more than one vessel of the circle. The aim of the present work was to study the variations of Cow, which could have an impact on cerebral blood supply during unilateral SCP. Methods and materials: We study 112 CoWs obtained from cadavers via routine dissection in the Department of Forensic Medicine of Medical University, Sofia. The external diameter of both vertebral arteries and all arteries that form Cow was measured with a caliper-gauge. Results: We identify the variations of CoW such as significant hypoplasy and/or lack of a branch of the circle. Bearing in mind the characteristics of the blood flow during unilateral SCP some of these variations were classified as significant during unilateral SCP. They were subdivided into groups according to most probable stroke site after unilateral SCP. Conclusions: Because of the high percent of the variations, hemodynamically significant during unilateral SCP, a suggestion for routine preoperative CT-angio of CoW could be made. Furthermore, an intraoperative follow-up with NIRO, transcranial Doppler, EEG, and so forth could also be recommended. (C) 2007 European Association for Cardio-Thoracic Surgery. Published by Elsevier B.V. All rights reserved.