This anomaly, persistent primitive trigeminal artery, is present in 0.1% to 0.6% of cerebral angiograms and is usually unilateral. In utero, the trigeminal artery supplies the basilar artery before development of the posterior communicating and vertebral arteries.

A PTA arises from the junction between petrous and cavernous ICA, and runs posterolaterally along the trigeminal nerve (41%), or crosses over or through the dorsum sellae (59%). Vertebral, posterior communicating and caudal basilar arteries are often hypoplastic.

There is an association with intracranial aneurysms and vascular malformations.

Credits Dr Jason Wenderoth