PRET: Patients Prone to Recurrence After Endovascular Treatment

Inclusion Criteria: * All patients presenting at least one aneurysm 'prone to recurrence after endovascular treatment' (PRET), defined for the sake of this study as: * PRET-1: One ruptured or unruptured aneurysm, never treated, with a dimension ≥10mm (longest axis, including thrombosed portions of large or giant aneurysms); for ruptured lesions, patients should be in WFNS grade I, II or III. * PRET-2: an Aneurysm presenting a major recurrence after previous coiling; and judged by the neurovascular team to require elective treatment. * The anatomy of the lesion is such that endovascular treatment is possible with both types of coils (not necessarily certain or probable) * The endovascular physician is content to use either type of coils (platinum or hydrogel-coated coils) but no other type of coils * Patient is 18 or older * Life expectancy is more than 2 years Exclusion Criteria: * Presence of other aneurysms requiring treatment during the same session * Patients with associated cerebral arteriovenous malformations * When parent vessel occlusion, without simultaneous endosaccular coiling of the aneurysm, is the primary intent of the procedure * Any absolute contraindication to endovascular treatment, angiography, or anaesthesia such as severe allergies to contrast or medications