COAST: Coiling of Aneurysms Smaller Than 5mm With Hypersoft® and Hydrogel Coils

This is a prospective, single-arm, multi-center post-marketing Study. The Study will commence as a single phase, with an optional second phase to follow at the discretion of the sponsor. Up to 300 eligible Subjects with small (\< 4.9 mm) intracranial aneurysms, who consent to Study participation, will be treated in Phase 1 with MicroVention HyperSoft® 3D and HyperSoft® Helical coils with or without balloon remodeling or stent assistance at the discretion of the treating physician. The operator, at his/her discretion, may choose to frame the aneurysm with HyperSoft® 3D or any other bare metal coil but must finish the remainder of the aneurysm with HyperSoft® 3D and/or HyperSoft® Helical coils. At the discretion of the sponsor, additional patients, up to 300 patients total for the overall Study, with eligible aneurysms will be enrolled into Phase 2. In Phase 2, the aneurysm must be framed with a HydroFrame® or HydroSoft® 3D coil and filled/finished primarily with hydrogel coils. The intent to treat is to frame, fill and finish with all hydrogel coils. However, at the discretion of the treating physician, a bare platinum coil may be used to fill or finish, as long as a minimum of 50% (in total coil length) of hydrogel coils are used. Data will be collected on immediate and post-treatment angiographic occlusion rates (RRGS), new peri-procedural imaging-confirmed hemorrhage or ischemic stroke, neurological morbidity and mortality rates, recurrence rates, bleeding rates, retreatment rates, serious adverse events, \>150 day angiographic occlusion rates (RRGS) and occlusion status. This will serve to establish the acute and sustained efficacy of EVT of small intracranial aneurysms with the specified microcoils, aided by balloon and/or stent remodeling where appropriate.