Unruptured Cerebral Aneurysm: Prediction of Evolution

The protocol has many assets. A prospective nationwide recruitment allows for the inclusion of a large cohort of patients with UIA. It will combine accurate clinical phenotyping and comprehensive imaging with CAWE screening. Besides, it will enable to exploit metadata and to explore new pathophysiological pathways of interest by crossing clinical, genetic, biological, and imaging information.

Inclusion Criteria : * Subject carrying unruptured, asymptomatic and untreated typical IA of bifurcation, measured on conventional imaging (MRI, CTA or DSA) between 3 and 7 mm of larger diameter. * Ability to be followed-up during 3 years decided in consensus multidisciplinary gathering. * Age \> 18 years old. Exclusion Criteria : * A failure to obtain informed consent * Contraindications for undergoing an MRI scan include : (heart pacemaker, a metallic foreign body (metal sliver) in their eye, or aneurysm clip in their brain, severe claustrophobia) * Contraindications for a gadolinium contrast medium injection (:eGFR below 30 mL/min/1.73 m2, Previous or pre-existing nephrogenic systemic fibrosis, Previous anaphylactic/anaphylactoid reaction to gadolinium containing contrast agent, Acutely deteriorating renal function, Pregnancy and breast-feeding) * A mycotic, fusiform-shaped, or dissecting IA, an IA in relation with an arteriovenous malformation * A family history of polycystic kidney disease, Ehlers-Danlos syndrome, Marfan's syndrom, fibromuscular dysplasia, or Moya Moya disease * Intra-cavernous UIA because the sinus cavernous that is fulfilled with venous blood precluded a reliable assessment of aneurysmal wall enhancement (AWE)