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Original research
Low prevalence of fetal-type posterior cerebral artery in patients with basilar tip aneurysms
  1. Mariana C Diogo1,
  2. Isabel Fragata1,
  3. Sara P Dias2,
  4. Joana Nunes3,
  5. Jaime Pamplona1,
  6. João Reis1
  1. 1Neuroradiology Department, Centro Hospitalar de Lisboa Central, Lisboa, Portugal
  2. 2Neurology Department, Centro Hospitalar de Lisboa Central, Lisboa, Portugal
  3. 3Neuroradiology Department, Centro Hospitalar de Vila Nova de Gaia/Espinho, Gaia, Portugal
  1. Correspondence to Dr Mariana Cardoso Diogo, Neuroradiology Department, Centro Hospitalar de Lisboa Central, Rua José António Serrano, Lisboa 1150–199, Portugal; mariana.cardoso.diogo{at}


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.

Materials and 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.

  • Aneurysm
  • Congenital
  • Intervention
  • Vessel Wall
  • Angiography

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