Persistent Primitive Trigeminal Artery is one of the persistent carotid-vertebro-basilar anastomoses. PTA arises from petrous-cavernous junction, runs posterolaterally along the trigeminal nerve, crosses over or through dorsum sella.
Two types of PTA have been described.
Saltzman Type I : PTA supplies the distal basilar artery. PComs are usually absent. The distal basilar artery is absent or hypoplastic. Distal vertebral arteries are also hypoplastic.
Saltzman Type II : PTA supplies the Superior Cerebellar Arteries, with PCAs supplied by the PCom.
TOF MRA images showed Saltzman type I PPTA, where the PTA is seen replacing the distal basilar artery.
Sagittal MIP MRA image showing the distal basilar artery completely supplied by the PTA.
The Tau sign, resembling a 'T' is classically described in the sagittal images.
