title: De novo giant A2 aneurysm following anterior communicating artery occlusion.
abstract: BACKGROUND
  De novo intracranial aneurysms are reported to occur with varying incidence after intracranial aneurysm treatment. They are purported to be observed, however, with increased incidence after Hunterian ligation; particularly in cases of carotid artery occlusion for giant or complex aneurysms deemed unclippable.
  
  
  METHODS
  We report a case of right-sided de novo giant A2 aneurysm 6 years after an anterior communicating artery (ACoA) aneurysm clipping. We believe this de novo aneurysm developed in part due to patient-specific risk factors but also a significant change in cerebral hemodynamics. The ACoA became occluded after surgery that likely altered the cerebral hemodynamics and contributed to the de novo aneurysm. We believe this to be the first reported case of a giant de novo aneurysm in this location. Following parent vessel occlusion (mostly of the carotid artery), there are no reports of any de novo aneurysms in the pericallosal arteries let alone a giant one. The patient had a dominant right A1 and the sudden increase in A2 blood flow likely resulted in increased wall shear stress, particularly in the medial wall of the A2 where the aneurysm occurred 2 mm distal to the A1-2 junction.
  
  
  CONCLUSIONS
  ACoA preservation is a key element of aneurysm surgery in this location. Suspected occlusion of this vessel may warrant closer radiographic follow-up in patients with other risk factors for aneurysm development.
authors.affiliation: Department of Neurosurgery, Helsinki University Hospital, Helsinki, Finland, USA ; Department of Neurosurgery, Loyola University Medical Center, Maywood, IL, USA.
authors.forename: Tarik F
authors.initials: TF
authors.lastname: Ibrahim
authors.affiliation: Department of Neurosurgery, Helsinki University Hospital, Helsinki, Finland, USA.
authors.forename: Ahmad
authors.initials: A
authors.lastname: Hafez
authors.affiliation: Department of Neurosurgery, Helsinki University Hospital, Helsinki, Finland, USA.
authors.forename: Hugo
authors.initials: H
authors.lastname: Andrade-Barazarte
authors.affiliation: Department of Neurosurgery, Helsinki University Hospital, Helsinki, Finland, USA.
authors.forename: Rahul
authors.initials: R
authors.lastname: Raj
authors.affiliation: Department of Neurosurgery, Helsinki University Hospital, Helsinki, Finland, USA.
authors.forename: Mika
authors.initials: M
authors.lastname: Niemela
authors.affiliation: Department of Neurosurgery, Helsinki University Hospital, Helsinki, Finland, USA.
authors.forename: Hanna
authors.initials: H
authors.lastname: Lehto
authors.affiliation: Department of Neuroradiology, Helsinki University Hospital, Helsinki, Finland, USA.
authors.forename: Jussi
authors.initials: J
authors.lastname: Numminen
authors.affiliation: Department of Neuroradiology, Helsinki University Hospital, Helsinki, Finland, USA.
authors.forename: Juha
authors.initials: J
authors.lastname: Jarvelainen
authors.affiliation: Department of Neurosurgery, Helsinki University Hospital, Helsinki, Finland, USA.
authors.forename: Juha
authors.initials: J
authors.lastname: Hernesniemi
keywords: A2; aneurysm; anterior communicating; de novo; giant; occlusion