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A vein of Galen aneurysmal malformation (VGAM) is a rare congenital arteriovenous malformation involving the choroidal system, which drains into the median prosencephalic vein, the embryonic precursor to the vein of Galen. VGAMs are distinct from other cerebral arteriovenous malformations which drain into an already formed, but dilated vein of Galen, an entity otherwise referred to as vein of Galen aneurysmal dilatation (VGAD). VGAM develops between the 6th and 11th week of gestation as a result of abnormal arteriovenous communication between the embryonic choroidal vessels and the median prosencephalic vein, which fails to involute as a result.