Flow-Diverter Treatment for Unruptured but Growing Vertebral Artery Dissecting Aneurysm Accompanied by Simultaneous Contralateral Vertebral Artery Dissection in the Acute Phase: A Case Report and Review of the Literature.

Unruptured but growing vertebral artery dissecting aneurysms (VADAs) pose a significant risk of rupture with devastating outcomes. Traditional treatments, such as parent artery occlusion or trapping, with or without bypass, can be challenging when the posterior inferior cerebellar artery (PICA), anterior spinal artery (ASA), or a concurrent contralateral lesion is involved. Although flow diverters (FDs) have recently been introduced as an alternative, their efficacy, safety, and optimal timing remain unclear. A 47-year-old male presented with a headache and was diagnosed with a right VADA. Follow-up imaging over two months revealed progressive aneurysmal formation. MRI also detected a new left vertebral artery (VA) dissection without an aneurysmal change. Due to PICA and ASA involvement and the contralateral lesion, FD placement was selected to preserve the parent artery. MRI on postoperative day (POD) one demonstrated luminal thrombosis outside the FD. Digital subtraction angiography (DSA) on POD seven and six months confirmed satisfactory occlusion of the VADA with preserved PICA and ASA, as well as stability of the contralateral lesion. FD placement can be an effective treatment option for managing unruptured but enlarging VADAs, enabling parent artery preservation while avoiding compromise of a coexisting contralateral lesion. Most previous studies provide limited guidance on the optimal timing of treatment. This report highlights the effectiveness of FD placement in the acute phase to prevent rupture.