title: Plasticity of circle of Willis: a longitudinal observation of flow patterns in the circle of Willis one week after stenting for severe internal carotid artery stenosis.
abstract: OBJECTIVE
  The purpose of the present study was to assess whether the direction of flow via the circle of Willis (CoW) changed after stenting for severe internal carotid artery (ICA) stenosis.
  
  
  METHODS
  65 patients (38 men, mean age 63.2 +/- 8.4 years, range 44-82) with a symptomatic ICA occlusion were investigated. Magnetic resonance angiography was performed prior to and 1 week after carotid artery stenting (CAS). The pattern in the CoW was assessed.
  
  
  RESULTS
  One third of the subjects (35.38%) had a significantly altered flow pattern in the CoW after unilateral CAS, including blocked ipsilateral A1 segment collateral (n = 4), blocked contralateral A1 segment collateral (n = 5), blocked ipsilateral posterior communicating artery (PCoA) segment collateral (n = 4), blocked ipsilateral A1 segment and P1 segment collateral (n = 1), opening of ipsilateral A1 segment collateral (n = 5), opening of ipsilateral PCoA segment collateral (n = 3) and opening of ipsilateral P1 segment collateral (n = 1).
  
  
  CONCLUSIONS
  CoW segmental hypoplasia is not a static feature. Willisian collateralization with recruitment of the CoW segment (A1, P1 and PCoA) may be blocked after CAS. CAS also leads to the opening of new willisian collateralization, either for relief of reperfusion pressure or for other hypoperfused areas.
authors.affiliation: Department of Neurology, Lo-Sheng Sanatorium, Taoyuan, Taiwan.
authors.forename: Yu-Ming
authors.initials: YM
authors.lastname: Chuang
authors.forename: Ching-Po
authors.initials: CP
authors.lastname: Lin
authors.forename: Ho-Fai
authors.initials: HF
authors.lastname: Wong
authors.forename: Yeu-Jhy
authors.initials: YJ
authors.lastname: Chang
authors.forename: Chien-Hung
authors.initials: CH
authors.lastname: Chang
authors.forename: Ting-Yu
authors.initials: TY
authors.lastname: Chang
authors.forename: Tai-Cheng
authors.initials: TC
authors.lastname: Wu
authors.forename: Hsiu-Chuan
authors.initials: HC
authors.lastname: Wu
authors.forename: Tsong-Hai
authors.initials: TH
authors.lastname: Lee
mesh_terms: D000222:Adaptation, Physiological / Q000502:physiology; D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D002343:Carotid Artery, Internal / Q000503:physiopathology; D016893:Carotid Stenosis / Q000175:diagnosis / Q000503:physiopathology / Q000628:therapy*; D002941:Circle of Willis / Q000503:physiopathology*; D005260:Female; D006801:Humans; D008137:Longitudinal Studies; D018810:Magnetic Resonance Angiography; D008297:Male; D008875:Middle Aged; D012039:Regional Blood Flow / Q000502:physiology; D012189:Retrospective Studies; D015607:Stents