Figure 2.

Possible variations involving paramedian perforating thalamic-mesencephalic arterial supply (according to Percheron's description) [7, 8]. I. The most common: many small perforating arteries arising bilaterally, from P1. IIb. The artery of Percheron: a single (asymmetrical) common trunk, arising from one P1 arterial segment. IIa. Multiple branches emerging (asymmetrically) from one P1 arterial segment. III. An arterial arcade is bridging the P1 segment of both PCAs, and the perforating arteries are arising from this arterial shunt. The actual case report: uncommon association of full fetal-type PCA (originating directly from the internal carotid artery) with Percheron's arterial variant. It was not possible to specify the particular anatomical arterial disposal (type IIb or IIa). (T, thalamus; M, mesencephalon; BA, basilar artery; PCA, posterior cerebral artery; P1, first arterial segment of the PCA; AOP, artery of Percheron; ICA, internal carotid artery.)