title: Unruptured intracranial aneurysms: natural history, clinical outcome, and risks of surgical and endovascular treatment.
abstract: BACKGROUND
  The management of unruptured intracranial aneurysms is controversial. Investigators from the International Study of Unruptured Intracranial Aneurysms aimed to assess the natural history of unruptured intracranial aneurysms and to measure the risk associated with their repair.
  
  
  METHODS
  Centres in the USA, Canada, and Europe enrolled patients for prospective assessment of unruptured aneurysms. Investigators recorded the natural history in patients who did not have surgery, and assessed morbidity and mortality associated with repair of unruptured aneurysms by either open surgery or endovascular procedures.
  
  
  RESULTS
  4060 patients were assessed-1692 did not have aneurysmal repair, 1917 had open surgery, and 451 had endovascular procedures. 5-year cumulative rupture rates for patients who did not have a history of subarachnoid haemorrhage with aneurysms located in internal carotid artery, anterior communicating or anterior cerebral artery, or middle cerebral artery were 0%, 2. 6%, 14 5%, and 40% for aneurysms less than 7 mm, 7-12 mm, 13-24 mm, and 25 mm or greater, respectively, compared with rates of 2 5%, 14 5%, 18 4%, and 50%, respectively, for the same size categories involving posterior circulation and posterior communicating artery aneurysms. These rates were often equalled or exceeded by the risks associated with surgical or endovascular repair of comparable lesions. Patients' age was a strong predictor of surgical outcome, and the size and location of an aneurysm predict both surgical and endovascular outcomes.
  
  
  CONCLUSIONS
  Many factors are involved in management of patients with unruptured intracranial aneurysms. Site, size, and group specific risks of the natural history should be compared with site, size, and age-specific risks of repair for each patient.
authors.affiliation: KA-MZ, ISUIA Coordinating Center, Mayo Clinic, Rochester, MN 55905, USA. wiebers.david@mayo.edu <wiebers.david@mayo.edu>
authors.forename: David O
authors.initials: DO
authors.lastname: Wiebers
authors.forename: J P
authors.initials: JP
authors.lastname: Whisnant
authors.forename: J
authors.initials: J
authors.lastname: Huston
authors.forename: I
authors.initials: I
authors.lastname: Meissner
authors.forename: R D
authors.initials: RD
authors.lastname: Brown
authors.forename: D G
authors.initials: DG
authors.lastname: Piepgras
authors.forename: G S
authors.initials: GS
authors.lastname: Forbes
authors.forename: K
authors.initials: K
authors.lastname: Thielen
authors.forename: D
authors.initials: D
authors.lastname: Nichols
authors.forename: W M
authors.initials: WM
authors.lastname: O'Fallon
authors.forename: J
authors.initials: J
authors.lastname: Peacock
authors.forename: L
authors.initials: L
authors.lastname: Jaeger
authors.forename: N F
authors.initials: NF
authors.lastname: Kassell
authors.forename: G L
authors.initials: GL
authors.lastname: Kongable-Beckman
authors.forename: J C
authors.initials: JC
authors.lastname: Torner
mesh_terms: D000367:Age Factors; D004621:Embolization, Therapeutic; D005260:Female; D005500:Follow-Up Studies; D006801:Humans; D002532:Intracranial Aneurysm / Q000473:pathology / Q000601:surgery / Q000628:therapy*; D008297:Male; D008875:Middle Aged; D011446:Prospective Studies; D012307:Risk Factors; D012422:Rupture, Spontaneous; D016896:Treatment Outcome