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