Intracranial venous drainage through spinal veins.

There is extensive collateral networking at the craniocervical junction with a substantial anatomical and functional continuity between the veins, venous sinuses, and venous plexuses of the brain and spine. The predominant pathway for intracranial blood outflow may depend on the level and degree of obstruction. We are presenting an unusual case of predominant egress of intracranial blood through enlarged spinal canal venous collaterals due to thrombosis of the intracranial venous sinuses. Awareness of this unique pattern of venous drainage of the cranium is important and should be considered in the differential diagnosis of spinal arteriovenous malformation (AVM) or arteriovenous fistula (AVF). Magnetic Resonance Venography (MRV) of the brain should be considered to exclude intracranial thrombosis in these cases.