Staged coiling and flow diversion for a ruptured persistent primitive hypoglossal artery aneurysm: illustrative case.

BACKGROUND: A persistent primitive hypoglossal artery (PPHA) is a rare embryonic carotid-vertebrobasilar anastomosis that can serve as the dominant posterior circulation inflow and predispose to aneurysm formation; optimal management remains unsettled. OBSERVATIONS: A 68-year-old woman presented with a World Federation of Neurosurgical Societies grade V subarachnoid hemorrhage resulting from a large, wide-necked aneurysm at the junction of the PPHA and vertebral artery. The contralateral vertebral artery was diminutive, and the anterior inferior cerebellar artery supplied the right posterior inferior cerebellar artery territory. To minimize acute-phase thromboembolic risk and prevent rebleeding, balloon-assisted coiling with hydrogel-coated coils was performed and Raymond-Roy class I occlusion (volume embolization ratio 20.2%) was achieved. The patient recovered to a modified Rankin Scale score of 1. Despite initial stability, recanalization occurred at 1 year. A FRED flow diverter was deployed by simple unsheathing without complications. Follow-up angiography showed complete occlusion at 6 months. LESSONS: In the context of PPHA anatomy with high posterior circulation dependence, a staged strategy-acute stentless coiling followed by delayed flow diversion-can balance immediate protection with durable reconstruction. A detailed anatomical evaluation (including perforators, vertebral artery caliber, and vascular variants) and antiplatelet optimization are essential. https://thejns.org/doi/10.3171/CASE2642.