Occipital artery to p3 segment of posterior inferior cerebellar artery bypass in treating a complex fusiform aneurysm

We provide a case report of a 58-year-old man who presented with a ruptured fusiform dissecting aneurysm located at the junction of the vertebral artery and posterior inferior cerebellar artery (PICA). Due to the lesion's complexity, a two-step approach was planned for revascularisation of PICA using the occipital artery (OA) prior to coiling embolisation. An end-to-side OA-PICA bypass was performed with implantation at the caudal loop of the p3 PICA segment. Fifteen days after the procedure, the aneurysm underwent stent-assisted coiling for successful obliteration of the aneurysm. The patient tolerated this procedure well and now at 1.5 years of follow-up remains free from any neurological deficits (modified Rankin Score 0). This case report illustrates one of the unique scenarios where both the vascular territory involved and morphological features of the aneurysm prohibited the use of more conventional means, necessitating the use of an arterial bypass graft for successful treatment of this lesion. As open vascular surgery is becoming less common in the age of endovascular coiling, our article uniquely reports on the combined use of both endovascular and microsurgical techniques to treat a complex aneurysm of the posterior circulation.