A novel endoleak classification for intracranial aneurysm flow diversion: A retrospective case series

Although flow diversion (FD) is safe and effective in the treatment of intracranial aneurysms, a subset tends to continue filling on serial angiography. Risk factors for failed flow diversion include old age, large aneurysm size, and overstenting an adjacent end-arterial vessel. The hemodynamic modes of persistent aneurysm filling, or 'endoleaks', after FD are poorly understood. This study aims to characterize the various types of endoleaks following aneurysmal FD.We performed a retrospective review of a prospectively maintained database of all endovascular procedures performed at a single institution between 2017 and 2021. Patients were included if they demonstrated evidence of unique modes of intracranial aneurysm filling after FD. Data regarding treatment, follow-up angiography, as well as clinical course were collected.Five patients (mean age 50 years, four females) were included with mean 19-month angiographic follow-up. Five major endoleak types are proposed: Type 1 - due to graft porosity (A - low flow, B - high flow), Type 2 -through an overstented branch vessel, Type 3 - via stent migration no longer covering aneurysmal neck, Type 4 - endoleak due to malapposition of the stent wall, and Type 5 - endoleak via collateralization from adjacent blood vessels. All endoleak types were represented, except for the Type 4 endoleak.We propose an endoleak classification scheme to describe the hemodynamic modes of failure following FD of intracranial aneurysms. Future studies are needed to evaluate the natural history of aneurysmal filling following FD and retreatment success according to endoleak type.