title: How often does an incomplete circle of Willis predispose to cerebral ischemia during closure of carotid artery? Postmortem and clinical imaging studies.
abstract: OBJECTIVE
  To evaluate the prevalence of anatomical variations in the circle of Willis predisposing to cerebral ischemia during intraoperative closure of a carotid artery.
  
  
  METHODS
  Anatomy of the cerebral arteries of 92 deceased was assessed by angiography and permanent silicone casts. Cerebral ischemia during closure of a carotid artery with patent contralateral internal carotid artery (ICA) was considered possible in cases of simultaneous nonfunctioning anterior communicating artery (diameter <0.5 mm) and ipsilateral posterior communicating artery (PComA) (diameter <0.5 mm or fetal type posterior cerebral artery). In cases of contralateral ICA occlusion, cerebral ischemia was considered possible if ipsilateral PComA was nonfunctioning.
  
  
  RESULTS
  Cerebral ischemia during closure of the right or left carotid artery with patent contralateral ICA was estimated to be possible in 16 (17.4%) and 13 (14.1%) cases. In cases of occluded contralateral ICA, the corresponding numbers were 55 (59.8%) and 49 (53.3%). A review of magnetic resonance and catheter angiographies also identified other variants of the circle of Willis with increased risk.
  
  
  CONCLUSIONS
  Incomplete circle of Willis predisposes approximately one-sixth of individuals to cerebral ischemia during transient closure of carotid artery but the risk is more than threefold in case of contralateral ICA occlusion.
authors: Diagnostic Medical Imaging Centre, Department of Radiology, Kuopio University Hospital and Kuopio University, Puijonlaaksontie 2, 70210, Kuopio, Finland. hannu.manninen@kuh.fi
authors: Hannu
authors: H
authors: Manninen
authors: Kimmo
authors: K
authors: Mäkinen
authors: Ritva
authors: R
authors: Vanninen
authors: Antti
authors: A
authors: Ronkainen
authors: Harri
authors: H
authors: Tulla
mesh_terms: D000293:Adolescent; D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D001344:Autopsy; D001921:Brain / Q000098:blood supply; D002545:Brain Ischemia / Q000209:etiology* / Q000503:physiopathology / Q000517:prevention & control; D002339:Carotid Arteries / Q000601:surgery*; D016893:Carotid Stenosis / Q000150:complications / Q000209:etiology / Q000503:physiopathology; D015984:Causality; D002533:Cerebral Angiography; D002560:Cerebrovascular Circulation / Q000502:physiology; D002941:Circle of Willis / Q000002:abnormalities* / Q000503:physiopathology*; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D008953:Models, Anatomic; D011183:Postoperative Complications / Q000209:etiology* / Q000503:physiopathology / Q000517:prevention & control; D013525:Surgical Instruments / Q000009:adverse effects; D014654:Vascular Patency / Q000502:physiology; D014656:Vascular Surgical Procedures / Q000009:adverse effects; D055815:Young Adult