title: Low prevalence of fetal-type posterior cerebral artery in patients with basilar tip aneurysms.
abstract: BACKGROUND
  Basilar tip aneurysms (BTA) are multifactorial in origin, with luminal forces playing a major role in their formation. Considering the reduced hemodynamic stress on the basilar apex in the fetal-type posterior cerebral artery (fPCA), we hypothesize that BTA should be less common in patients with this variant.
  
  
  OBJECTIVE
  To investigate, in a retrospective case-control study, the frequency of fPCA in patients with and without BTA.
  
  
  METHODS
  We collected clinical and imaging data from consecutive patients with BTA undergoing catheter angiography between July 2010 and July 2015, and from a randomly selected, age- and sex-matched non-BTA control population from our prospective database. Anatomical variants of the distal basilar artery region were assessed in the two groups and compared using parametric and non-parametric tests.
  
  
  RESULTS
  Fifty-nine BTA cases and 337 controls were included. fPCA was present in 3% of patients with BTA and 23% in the control group (p<0.001; OR=0.11, 95% CI 0.03 to 0.48). Basilar tip disposition was cranial in 49% of BTA and 63% of non-BTA cases (p=0.04; OR=0.57, 95% CI 0.33 to 0.99); a caudal disposition was found in 24% and 6% of cases, respectively (p<0.001; OR=4.65, 95% CI 2.21 to 9.80).
  
  
  CONCLUSIONS
  We found a statistically significant association between the absence of fPCA and BTA. Our findings underline the importance of hemodynamic stress in the formation of intracranial aneurysms, and suggest that fPCA is a protective variant for formation of BTA.
authors.affiliation: Neuroradiology Department, Centro Hospitalar de Lisboa Central, Lisboa, Portugal.
authors.forename: Mariana C
authors.initials: MC
authors.lastname: Diogo
authors.affiliation: Neuroradiology Department, Centro Hospitalar de Lisboa Central, Lisboa, Portugal.
authors.forename: Isabel
authors.identifier: http://orcid.org/0000-0002-7037-7458
authors.initials: I
authors.lastname: Fragata
authors.affiliation: Neurology Department, Centro Hospitalar de Lisboa Central, Lisboa, Portugal.
authors.forename: Sara P
authors.identifier: http://orcid.org/0000-0002-0115-4840
authors.initials: SP
authors.lastname: Dias
authors.affiliation: Neuroradiology Department, Centro Hospitalar de Vila Nova de Gaia/Espinho, Gaia, Portugal.
authors.forename: Joana
authors.identifier: http://orcid.org/0000-0003-2092-828X
authors.initials: J
authors.lastname: Nunes
authors.affiliation: Neuroradiology Department, Centro Hospitalar de Lisboa Central, Lisboa, Portugal.
authors.forename: Jaime
authors.identifier: http://orcid.org/0000-0001-6920-8297
authors.initials: J
authors.lastname: Pamplona
authors.affiliation: Neuroradiology Department, Centro Hospitalar de Lisboa Central, Lisboa, Portugal.
authors.forename: João
authors.identifier: http://orcid.org/0000-0002-7151-4063
authors.initials: J
authors.lastname: Reis
mesh_terms: D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D001488:Basilar Artery / Q000000981:diagnostic imaging*; D016022:Case-Control Studies; D002533:Cerebral Angiography / Q000379:methods; D005260:Female; D006439:Hemodynamics / Q000502:physiology; D006801:Humans; D002532:Intracranial Aneurysm / Q000000981:diagnostic imaging* / Q000453:epidemiology*; D008297:Male; D008875:Middle Aged; D020769:Posterior Cerebral Artery / Q000000981:diagnostic imaging*; D015995:Prevalence; D011446:Prospective Studies; D012189:Retrospective Studies
keywords: Aneurysm; Angiography; Congenital; Intervention; Vessel Wall