title: Clinical characteristics and preferential location of intracranial mirror aneurysms: a comparison with non-mirror multiple and single aneurysms.
abstract: BACKGROUND
  The purpose of our study was to compare the clinical characteristics and preferential localization of aneurysms in three patient groups: single aneurysm, non-mirror multiple aneurysms, and mirror aneurysms.
  
  
  METHODS
  We retrospectively reviewed the clinical and radiological data of 2223 consecutive patients harboring 3068 aneurysms registered at the Toronto Western Hospital between May 1994 and November 2010. The patients were divided into single, non-mirror multiple, or mirror aneurysm groups. Expected incidences of mirror aneurysms at each location were calculated on the basis of the single aneurysm incidences at each location.
  
  
  RESULTS
  Patients with mirror aneurysms (n = 197) did not differ from patients with non-mirror multiple aneurysms (n = 392) in having female predominance (81.7 vs. 76.3 %) or a family history of intracranial aneurysm (20.5 vs. 17.6 %). When compared with expected incidences at each location, mirror aneurysms were more frequently found at the cavernous internal carotid artery (30 vs. 11.5 %) (p < 0.0001). Mirror aneurysms involving the posterior circulation were less frequent (6.7 %) than aneurysms in the single (19.6 %) or non-mirror multiple aneurysm groups (18.9 %) (p < 0.05).
  
  
  CONCLUSIONS
  Patients with mirror aneurysms had similar clinical characteristics to non-mirror multiple aneurysm patients. Mirror aneurysms showed a predilection for the cavernous carotid artery, whereas they were comparatively rare in the posterior circulation.
authors.affiliation: Division of Neuroradiology, Department of Medical Imaging, Toronto Western Hospital, University of Toronto, 399 Bathurst St., 3 McLaughlin Wing, Toronto, ON, M5T 2S8, Canada.
authors.forename: Young-Jun
authors.initials: YJ
authors.lastname: Lee
authors.forename: Tiago
authors.initials: T
authors.lastname: Parreira
authors.forename: Charles C
authors.initials: CC
authors.lastname: Matouk
authors.forename: Ravi
authors.initials: R
authors.lastname: Menezes
authors.forename: Daniel M
authors.initials: DM
authors.lastname: Mandell
authors.forename: Karel G
authors.initials: KG
authors.lastname: terBrugge
authors.forename: Robert A
authors.initials: RA
authors.lastname: Willinsky
authors.forename: Timo
authors.initials: T
authors.lastname: Krings
mesh_terms: D000368:Aged; D002533:Cerebral Angiography; D005260:Female; D006801:Humans; D002532:Intracranial Aneurysm / Q000145:classification* / Q000000981:diagnostic imaging*; D008297:Male; D008875:Middle Aged; D012189:Retrospective Studies; D014057:Tomography, X-Ray Computed