Pial arteriovenous fistula with multiple venous aneurysms resembling a vein of Galen aneurysmal malformation.

Pial arteriovenous fistulas (pAVFs) are abnormal vascular connections between arteries and the cranial venous system on the surface of the brain in the pia mater. Unlike vein of Galen aneurysmal malformations (VGAM), they lack a true vascular nidus, and may only indirectly involve the vein of Galen. We describe a case of a pAVF with a presentation resembling a VGAM and discuss the importance of considering a pAVF as a possible differential diagnosis to a VGAM when the vein of Galen is dilated.