Unruptured Cerebral Aneurysm: Prediction of Evolution

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)