title: Anatomic variations in the anterior circulation of the circle of Willis in cadaveric human brains.
abstract: OBJECTIVE
  The Cycle of Willis unites the internal carotid and vertebrobasilar system and maintains the stability of blood supply to the brain. This present study aims to analyze the anatomic variations in the anterior part of the Cycle of Willis.
  
  
  METHODS
  Forty five formalin-preserved human brains (90 cerebral hemispheres) with intact dura mater from Chinese adults were dissected under the surgical microscope. The anterior components of the Circle of Willis were observed and measured. Anatomic variations of this segment were observed and photographed. The data collected in this investigation was statistically analyzed.
  
  
  RESULTS
  In approximately 13.3% (6/45) of all cerebral samples, a caliber difference of ≥ 0.5 mm was noted between the left A1 and the right segments. The A2 segments of left and right hemispheres were derived from the contralateral A1 segment in 6.7% (3/45) of the brain specimens. Simple anterior communicating artery (ACoA) was observed in 37.8% (17/45) whereas complex ACoA was noted in 60% (27/45) of cerebral samples.
  
  
  CONCLUSIONS
  As it demonstrates the anatomic variations of ACAC, all surgical approaches should be performed after angiographic demonstrations. Understanding of these anatomic variations plays a pivotal role in neurovascular procedures.
authors.affiliation: Shanghai JiaoTong University Affiliated Sixth People's Hospital Shanghai 200233, China.
authors.forename: Yuhui
authors.initials: Y
authors.lastname: Cui
authors.affiliation: Shanghai JiaoTong University Affiliated Sixth People's Hospital Shanghai 200233, China.
authors.forename: Tao
authors.initials: T
authors.lastname: Xu
authors.affiliation: Shanghai JiaoTong University Affiliated Sixth People's Hospital Shanghai 200233, China.
authors.forename: Jiong
authors.initials: J
authors.lastname: Chen
authors.affiliation: Shanghai JiaoTong University Affiliated Sixth People's Hospital Shanghai 200233, China.
authors.forename: Hengli
authors.initials: H
authors.lastname: Tian
authors.affiliation: Shanghai JiaoTong University Affiliated Sixth People's Hospital Shanghai 200233, China.
authors.forename: Heli
authors.initials: H
authors.lastname: Cao
keywords: Circle of Willis; anterior circulation; microanatomy; variation