The persistent trigeminal artery (PTA) is the most frequent carotidvertebrobasilar anastomosis.It arises from the precavernous or cavernous internal carotid artery(ICA) and anastomoses to the mid portion of the basilar artery (BA).As mentioned,it can arise more proximally,mimicking a persistent otic artery.Reported MRA incidence is approximately 1％.rnAccording to its course from the ICA to the BA,there are lateral and medial types.The two types can be distinguished by caudo-cranial projection but not by conventional angiography,which is usually taken with anteroposterior and lateral projections.Lateral is more common than medial PTA and runs posteriorly parallel to the trigeminal nerve.