Persistent embryonic veins in the arteriovenous malformation of the diencephalon.

The diencephalic arteriovenous malformation is produced by the posterior cerebral, posterior choroidal, and anterior choroidal arteries. The abnormal arterialised vessels seen in these malformation represent dorsal and ventral diencephalic veins. The drainage of the shunted blood is primarily into the transverse sinus. This is later diverted medially into the great cerebral vein, with the formation of the basal vein. The medial drainage, in keeping with the normal developmental pattern, is seen frequently. The presence and locations of angiomas are very variable and do not follow any predictable pattern.