Introduction Balloon-assisted coil embolization of proximal posterior inferior cerebellar artery (PICA) aneurysms may be limited by the inferiorly oriented, acutely angulated origin of the PICA from the vertebral artery. The aim of this study is to evaluate retrograde access to the PICA via the contralateral vertebral artery or the posterior communicating artery.

Methods Twenty-nine proximal PICA aneurysms treated by balloon remodeling with navigation of the balloon in the PICA via the contralateral vertebral artery or posterior communicating artery were found in our database between January 2007 and December 2013 and were reviewed.

Results Access to the PICA was made via the contralateral vertebral artery in 26 patients (90%), six of them (23%) with a hypoplastic V4 segment. In three patients (10%) the retrograde approach was made via the posterior communicating artery. After balloon remodeling, additional stenting was performed in 16 patients (55%). The complication rate was 3% (1 acute stent thrombosis). Grade 0 or 1 occlusion was obtained in all patients at completion angiography. No recurrence was found during follow-up.

Conclusions Retrograde access to the PICA to perform balloon-assisted coil embolization of proximal PICA aneurysms with or without additional stenting after coiling is safe and effective. Hypoplastic V4 segment of the contralateral vertebral artery is not a contraindication.