Fig. 4.

Anatomic variations of the arterial supply to the paramedian thalamic-mesencephalic region as described by Percheron [4]. a Common variation, many small perforating vessels arising from the P1 segments of both posterior cerebral arteries. b Artery of Percheron variant, arising from the P1 tract of a single posterior cerebral artery and supplying both thalami. c Arcade variant, with several small perforating branches arising from a single artery that bridges the P1 segments of both posterior cerebral arteries.