Risk of Rupture of Small Anterior Communicating Artery Aneurysms Is Similar to Posterior Circulation Aneurysms
Authors: Bijlenga Philippe , Ebeling Christian , Jaegersberg Max , Summers Paul , Rogers Alister , Waterworth Alan , Iavindrasana Jimison , Macho Juan , Pereira Vitor Mendes , Bukovics Peter , Vivas Elio , Sturkenboom Miriam C.J.M. , Wright Jessica , Friedrich Christoph M. , Frangi Alejandro , Byrne James , Schaller Karl , Rufenacht Daniel ,   Collaborators From the @neurIST Investigators, Narata Ana Paula , Clarke Alison , Yarnold Julia , Kover Ferenc , Schatlo Bawarjan , Hudak Stephan , Teta Patrick , Blasco Jordi , Gonzalez Ana Marcos , Lovblad Karl-Olof , Coley Stuart , Dòczi Tamas , Risselada Roelof , Sola Theresa , Lawford Patricia , Patel Umang , Singh Pankaj , Wickins Jeremy , Elger Bernice , Beyleveld Derick , Wood Steven , Hasselmeyer Peer , Arbona Antonio , Meyer Rodolphe , Hose Rod , Lonsdale Guy , Hofmann-Apitius Martin ,   Investigators,   Project Board:, Frangi Alejandro , Bijlenga Philippe , Hofmann-Apitius Martin , Hose Rod , Lonsdale Guy , Arbona Antonio , Hasselmeyer Peer , Rüfenacht Daniel ,   Article writing team:, Bijlenga Philippe , Summers Paul , Jägersberg Max , Rogers Alister , Schaller Karl , Byrne James ,   Ethical and legal review committee:, Wright Jessica , Wilkins Jeremy , Beyleveld Derick , Elger Bernice ,   Information platform development and maintenance:, Waterworth Alan , Wood Steven , Iavindrasana Jimison , Meyer Rodolphe , Friedrich Christoph , Ebeling Christian ,   Epidemiology and statistics:, Ebeling Christian , Bijlenga Philippe , Risselada Roelof , Friedrich Christoph , Sturkenboom Miriam CJM ,   Participating Centers (In Order of Number of Recruited Patients), Bijlenga Philippe , Jägersberg Max , Rogers Alister , Schatlo Bawarjan , Teta Patrick , Schaller Karl , Mendes-Pereira Vitor , Gonzalez Ana Marcos , Narata Ana Paula , Lovblad Karl O , Rüfenacht Daniel A. , Yarnold Julia , Summers Paul , Clarke Alison , Zilani Gulam , Byrne James , Macho Juan , Blasco Jordi , Bukovics Peter , Kover Ferenc , Hudak Istvan , Doczi Tamas , Risselada Roelof , Sturkenboom Miriam CJM , Singh Pankaj , Waterworth Alan , Patel Umang , Coley Stuart , Lawford Patricia , Sola Teresa , Vivas Elio 
Published: July 2013

Background and Purpose—
According to the International Study of Unruptured Intracranial Aneurysms (ISUIA), anterior circulation (AC) aneurysms of <7 mm in diameter have a minimal risk of rupture. It is general experience, however, that anterior communicating artery (AcoA) aneurysms are frequent and mostly rupture at <7 mm. The aim of the study was to assess whether AcoA aneurysms behave differently from other AC aneurysms.

Methods—
Information about 932 patients newly diagnosed with intracranial aneurysms between November 1, 2006, and March 31, 2012, including aneurysm status at diagnosis, its location, size, and risk factors, was collected during the multicenter @neurIST project. For each location or location and size subgroup, the odds ratio (OR) of aneurysms being ruptured at diagnosis was calculated.

Results—
The OR for aneurysms to be discovered ruptured was significantly higher for AcoA (OR, 3.5 [95% confidence interval, 2.6–4.5]) and posterior circulation (OR, 2.6 [95% confidence interval, 2.1–3.3]) than for AC excluding AcoA (OR, 0.5 [95% confidence interval, 0.4–0.6]). Although a threshold of 7 mm has been suggested by ISUIA as a threshold for aggressive treatment, AcoA aneurysms <7 mm were more frequently found ruptured (OR, 2.0 [95% confidence interval, 1.3–3.0]) than AC aneurysms of 7 to 12 mm diameter as defined in ISUIA.

Conclusions—
We found that AC aneurysms are not a homogenous group. Aneurysms between 4 and 7 mm located in AcoA or distal anterior cerebral artery present similar rupture odds to posterior circulation aneurysms. Intervention should be recommended for this high-risk lesion group.