title: The circle of Willis in healthy older persons.
abstract: BACKGROUND
  The current indication for carotid surgery is based upon the percentage of stenosis of the internal carotid artery. This approach shows many limitations, one of which is to presume the anatomical completeness of the circle of Willis in all patients who are evaluated. On the contrary, there is increasing evidence of a great natural variability in the configuration of the circle of Willis.
  
  
  METHODS
  The aim of the present paper was to investigate, by magnetic resonance angiography, the variability of the circle of Willis in a cohort of 118 healthy older persons.
  
  
  RESULTS
  The circle of Willis showed an entirely complete configuration in 47% of the subjects, a complete configuration of its anterior part in 90% of the subjects, and a complete configuration of its posterior part in 48.5% of the subjects.
  
  
  CONCLUSIONS
  These findings confirm the great variability of the circle of Willis even in healthy older persons and suggest that, in indicating carotid surgery, the configuration of the circle of Willis should also be taken into account.
authors.affiliation: Department of Cardiovascular Medicine, Don Gnocchi Foundation, Florence, Italy.
authors.forename: C
authors.initials: C
authors.lastname: Macchi
authors.forename: R Molina
authors.initials: RM
authors.lastname: Lova
authors.forename: B
authors.initials: B
authors.lastname: Miniati
authors.forename: M
authors.initials: M
authors.lastname: Gulisano
authors.forename: C
authors.initials: C
authors.lastname: Pratesi
authors.forename: A A
authors.initials: AA
authors.lastname: Conti
authors.forename: G F
authors.initials: GF
authors.lastname: Gensini
mesh_terms: D000367:Age Factors; D000368:Aged; D000369:Aged, 80 and over; D000375:Aging / Q000502:physiology*; D016893:Carotid Stenosis / Q000175:diagnosis; D002560:Cerebrovascular Circulation / Q000502:physiology; D002941:Circle of Willis / Q000033:anatomy & histology* / Q000502:physiology*; D015331:Cohort Studies; D005260:Female; D006801:Humans; D018810:Magnetic Resonance Angiography; D008297:Male; D011446:Prospective Studies; D012016:Reference Values; D018570:Risk Assessment; D012680:Sensitivity and Specificity; D012737:Sex Factors; D020521:Stroke / Q000175:diagnosis