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