Abstract
Vertebrobasilar dolichoectasia (VBD) is a rare, progressive disorder characterized by significant expansion, elongation, and tortuosity of the vertebrobasilar arteries. This case series introduces a novel imaging sign observed in three patients with clinical manifestations of VBD. The presence of outside-stent flow (OSF) may serve as a potential predictor for aneurysm recurrence in VBD following endovascular intervention. Furthermore, OSF could indicate the need for embolization of the contralateral vertebral artery after stenting, with or without coil embolization, in patients with VBD aneurysms.