Persistent Trigeminal Artery (PTA), Tau sign

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. 

Another case of Fenestrated Left SCA - MRA

Strange..another case of fenestrated left Superior cerebellar artery..another patient.

Fenestration of Left Superior Cerebellar Artery

Looks like a fenestrated left Superior Cerebellar Artery, incidental finding  in a patient evaluated for right hemiparesis.

Similar cases:

1. Acta Neurochir (Wien). 1991;109(1-2):66-71.

Anomalies of the P1 segment of the posterior cerebral artery: early bifurcation or duplication, fenestration, common trunk with the superior cerebellar artery.

Caruso G, Vincentelli F, Rabehanta P, Giudicelli G, Grisoli F.

http://www.ncbi.nlm.nih.gov/pubmed/2068971?dopt=Abstract