Introduction Basilar fenestration aneurysms are rare, challenging intracranial vascular lesions with atypical anatomy. The posterior circulation represents a difficult therapeutic dilemma due to the close proximity of crucial life sustaining brainstem structures. Flow diverter technology became available a few years ago, however, its use has been limited in the posterior circulation.

Methods We present the case of a 49-year-old female with a history of smoking, who was diagnosed with a symptomatic, large vertebrobasilar junction (VBJ) aneurysm. Initially thought to be a proximal basilar dilatation, the aneurysm was later found to arise from an obscured and distended basilar fenestration. The small caliber fenestration limbs were the only access to the distal basilar artery, but stretched laterally and concealed by the aneurysm fundus.

Results We successfully treated this complex lesion by flow diverter deployment through one of the obscured fenestration limbs, followed by coiling of the aneurysm fundus, and sacrificing the contralateral vertebral artery. A six-month follow-up angiogram showed remodeling of the basilar artery, and complete occlusion of the aneurysm. The patient had an excellent clinical outcome.

Conclusion To our knowledge, direct flow diverter deployment in a small fenestration limb for the treatment of a VBJ aneurysm with reconstruction of the basilar artery has not been reported. Careful diagnostic workup, multidisciplinary discussions, and the innovative use of versatile endovascular technology were crucial to achieve an optimal result in our case. Further studies are necessary to establish the safety and long-term efficacy of this treatment method.

Disclosures G. Toth: None. M. Bain: None. F. Hui: None.