Hydrogel Balloon Assisted Intracranial Aneurysm Coiling Registry

Inclusion Criteria: * Patient is 18-80 years of age. * Patient has a documented, previously treated or untreated saccular intracranial aneurysm, 4- 20 mm unruptured or ruptured, suitable for treatment with balloon assisted coil embolization. * Target aneurysm has a neck ≥4mm or the largest diameter to neck ratio of 2 or less. * Patient has a Hunt and Hess Score of 3 or less. * Patient has a premorbid mRS of 3 or less. * Patient or patient's legally authorized representative has provided written informed consent. * Patient is willing to and can comply with study follow-up requirements. Exclusion Criteria: * Inability to obtain informed consent. * Patient is \<18 or \>80 years of age. * Target aneurysm is dissecting, fusiform, mycotic, or arteriovenous malformation-related. * Aneurysm that was treated previously with stent-assisted coiling. * Implantation of the stent after the balloon-assisted coiling or combined stent and balloon assisted coiling. * Target aneurysm is deemed unsuitable for balloon-assisted coiling by the treating physician prior to the procedure. * Target aneurysm will be treated with a total coil length comprised of less than 80% second generation MicroVention Hydrogel Coils. * Balloon-assisted coiling will be performed using a balloon catheter other than the MicroVention Scepter balloon (Scepter C, Scepter XC, any future Scepter configurations). * Patients in which the target aneurysm is planned not to be coiled in one procedure (i.e. staged procedure). * Patients with more than one aneurysm that requires treatment. (However, a second small low risk aneurysm that does not require therapy may be allowed.) * Patients with a life expectancy of ≤ 9 months.