Fenestra obscura: Flow diverter reconstruction of a complex vertebrobasilar aneurysm through an obscured fenestration limb: Technical case report

BACKGROUND AND IMPORTANCE: Basilar fenestration aneurysms are rare, challenging intracranial vascular lesions with atypical anatomy. The posterior circulation represents a difficult therapeutic dilemma because of the close proximity of crucial life-sustaining brainstem structures. The use of flow diverter technology has been very limited in posterior circulation vessels. CLINICAL PRESENTATION: We present the case of a 49-year-old female patient, who was diagnosed with a symptomatic large vertebrobasilar junction aneurysm, which was initially thought to be a proximal basilar dilatation. The aneurysm was later verified to arise from the proximal end of a basilar fenestration, distended by the aneurysm fundus. The small-caliber fenestration limbs were the only connection to the distal basilar artery, but were stretched laterally and concealed by the aneurysm fundus. This complex lesion was successfully treated by flow diverter deployment through one of the fenestration limbs, followed by coiling of the aneurysm fundus, and sacrificing the contralateral vertebral artery. A 6-month follow-up angiogram showed remodeling of the basilar artery and complete occlusion of the aneurysm with good clinical outcome. Careful diagnostic workup, multidisciplinary discussions, and the innovative use of versatile endovascular technology were crucial to achieve an optimal result in this case. CONCLUSION: This is the first report of a successful basilar artery reconstruction for the treatment of a large atypical vertebrobasilar junction fenestration aneurysm by deployment of a flow diverter device directly in a small, obscured fenestration limb.