Microsurgical Study on the Circle of Willis in Korean Adults

ABSTRACT

Anatomical information of the circle of Willis is important in evaluating the various cerebrovascular diseases and surgical procedures. In this study, we present the anatomical structures of the circle of Willis in 54 Korean adults. The authors observed the morphological characteristics of the vasculature, the incidence of deficiency or incompleteness in the circle and clinical considerations. Measurements of the outer diameter and the length of each arterial segments were performed. Number and the origin of perforators from individual arteries were also oserved. Results of this study were as followings. Normal circles of Willis was oserved in 35 cases(64.81%) and abnormal circles in 19 cases(35.9%). 2) Incidental detection of aneurysms occurred in 5 cases(9.26%). 3) Frequency of anomalies were most commonly observed in the anterior communicating arteries(N=16, 20.37%). 4) A string-like artery was most frequently observed in te post-erior communicating artery(N=11, 20.37%). 5) Anomalous origin of the P1 segment of the posterior cerebral artery was observed, fetal type was in 12 cases(22.2%) and transitional typ was in 3 cases(5.55%) respectively. 6) The longest artery was the A1 segmnt of the anterior cerebral artery;the second, posterior communicating artery;the third, P1 segment of the posterior cerebral artery;and the shortest, anterior communicating artery. 7) The outer diameters of the basilar artery and internal carotid artery were almost, equal, A1 segment was half of ICA, AcoA was two thirds of A1 segment, PcoA was half of P1 segment and P1 segment was two thirds of the basilar artery. There were difference the anterior and posterior portion of the circle Willis. In the anterior communicating arteries, duplicated structure were frequently found. And also, inequality in the outer diameter of both A1 segmnts was observed. String-like arteries were often revealed in the posterior communicating arteries. Anomalous origin of P1 segments that may be persistant embryonic derivatives were frequently demonstrated in posterior cerebral arteries.