Persistent trigeminal artery (PTA) : Is The most common persistent carotid-verebrobasilar anastmosis with cavernous ICA to basilar artery (BA) anastmosis.
Saltzman type I: PTA supplies the distal vertebrobasilar arteries. Absent PCOM. The caudal BA is absent or hypoplastic with hypolplastic distal vertebral arteries.
Saltzman type II: PTA supplies the superior cerebellar arteries with the PCAs are supplied via the PCOM.