Carotid siphon geometry and variants of the circle of Willis in the origin of carotid aneurysms

Arq Neuropsiquiatr. 2012 Dec;70(12):917-21. doi: 10.1590/s0004-282x2012001200003.


This study evaluated anatomical variants in the carotid siphon and of the circle of Willis in patients with aneurysms. We performed a retrospective analysis of cerebral angiographies. The Control Group was composed of patients without aneurysms. Posterior communicating artery (PcomA) aneurysms were more common in women (p<0.05), and the anterior communicating artery (AcomA) aneurysms in men (p<0.1). The incidence of fetal-type PcomA was higher in cases with co-occurring PcomA aneurysm (24 versus 8%, p<0.05). Patients with AcomA aneurysm had higher incidence of A1 hypoplasia (p<0.0001, OR=32.13, 95%CI 12.95-79.71) and lower frequency of fetal-type PcomA compared to their control counterparts (p=0.0125). The angle of carotid siphon was narrower in patients with PcomA aneurysm (27.3±19.1 versus 34.8±22.6, p=0.028). In conclusion, a narrower carotid siphon or the presence of fetal-type PcomA or A1 hypoplasia may cause hemodynamic stress, thereby promoting the formation of aneurysms in susceptible individuals.

MeSH terms

  • Carotid Artery, Internal / diagnostic imaging*
  • Carotid Artery, Internal / pathology
  • Case-Control Studies
  • Cerebral Angiography
  • Circle of Willis / diagnostic imaging
  • Circle of Willis / pathology*
  • Female
  • Humans
  • Intracranial Aneurysm / diagnostic imaging
  • Intracranial Aneurysm / etiology*
  • Male
  • Middle Aged
  • Retrospective Studies