Persistent trigeminal artery arising from the arterial ring/fenestration of the cavernous segment of the internal carotid artery.

A persistent trigeminal artery (PTA) is the most common carotid-vertebrobasilar anastomosis, usually arising from the cavernous or precavernous segment of the internal carotid artery (ICA) and connecting to the distal basilar artery. There are two types of PTA, lateral and medial. We present the first case of a lateral-type PTA arising from the large arterial ring/fenestration of the cavernous segment of the left ICA with findings from both magnetic resonance angiography and selective catheter angiography.