Vascular variations associated with intracranial aneurysms

the first time as the famous 'circle of Willis' in the eighteenth century (25).Classically, a symmetrical and complete Willis pattern accounts for only 30-50% of individuals in the population (1,8,10,27).The arteries constituting it may show different variations depending on their hypoplasia, aplasia and fenestration, duplication, trifurcation.These variations may play a considerable role in the development of an aneurysm, █ INTRODUCTION T he carotid and vertebrobasilar systems are connected to each other by a polygonal anastomosis channel system that is called 'circulus arteriosus' at the base of the brain.Although Thomas Willis made the first attempt to attribute a function to this anatomy that he described in 1664; his description of the brain became accepted as definitive, appearing in the Bibliotheca Anatomica of 1774-1777 for AIm: To investigate the vascular variations in patients with intracranial aneurysm in circle of Willis. mATERIAl and mEThODS:We used the data on 128 consecutive intracranial aneurysm cases.Cerebral angiography images were analyzed retrospectively.Arteries were grouped as anterior cerebral arterial system (ACS), posterior cerebral arterial system (PCS) and middle cerebral arterial system (MCS) for grouping vascular variations.Lateralization, being single/multiple, gender; and also any connection with accompanying aneurysms' number, localization, dimension, whether bleeding/incidental aneurysm has been inspected.RESUlTS: Variations were demonstrated in 57.8% of the cases.The most common variation was A1 variation (34.4%).The rate of variations was 36.7%, 24.2% and 10.2% respectively in ACS, PCS and MCS.MCS variations were significantly higher in males.Anterior communicating artery (ACoA) aneurysm observance rates were significantly higher and posterior communicating artery (PCoA) aneurysm and middle cerebral artery (MCA) aneurysm observance rates were significantly lower when compared to 'no ACS variation detected' cases.In 'PCS variation detected' cases, PCoA aneurysm observance rates and coexistence of multiple variations were significantly higher.CONClUSION: The rate of vascular variations in patients with aneurysms was 57.8%.Arterial hypoplasia and aplasia were the most common variations.ACS was the most common region that variations were located in; they were mostly detected on the right side.Coexistence of ACoA aneurysm was higher than PCoA and MCA aneurysms.In the PCS variations group, PCoA aneurysms were the most common aneurysms that accompanying the variation and multiple variations were more common than in the other two groups.The variations in MCS were most common in males.