A case of a type II proatlantal artery with arteriovenous malformation.

We describe a 64-year-old woman evaluated with angiography a case of persistence of a proatlantal artery (type II) with an arteriovenous malformation associated to the posterior cerebral artery. This association has been reported once in the literature consulted. The proatlantal artery arises from external carotid artery, cranial to the origin of facial artery at the level of C4 vertebra, anteromedial to the internal carotid artery, laying on it during its course cranial, lateral and posterior. After making a loop at the level of the transverse process of C3 vertebra, it enters into the transverse foramen of C3 vertebra and continuing its course, through the transverse foramen of C2 and C1 vertebra, as vertebral artery. Winds behind the superior articular process of the atlas enters the skull through the foramen magnum and, at the lower border of the pons, joins with the vessel of the opposite side to form the basilar artery. The internal carotid artery is normal. This variation is associated with congenital arteriovenous malformations that represent the persistence of an embryonic pattern of congenital vessels.