Persistent primitive trigeminal artery associated with posterior communicating artery aneurysm and hypoplastic vertebral artery.

We report a patient who presented with headache due to diffuse subarachnoid hemorrhage. A four-vessel angiogram revealed a left posterior communicating artery aneurysm with fetal origin, persistent primitive trigeminal artery and hypoplastic vertebral artery on the same side. This association was considered coincidental and co-existence of a saccular aneurysm with an anatomical variation of intracranial vasculature is briefly discussed.