Spinal Vascular Malformations
The spinal vascular malformations are in many ways analogous to their intracranial counterparts. Lesions characterized by high flow shunts include spinal arteriovenous fistulas (AVF) and spinal arteriovenous malformations (AVM). The most common classification scheme for spinal vascular malformations uses the Type 1 to 4 classification system, though other classification schema exist.
Type 1 lesions are dural AVFs in which a radiculomeningeal artery forms a fistulous communication with dural veins at the nerve root sleeve, and result in subsequent arterialization of the perimedullary venous plexus. Type 2 AVMs have an intramedullary nidus with variable anterior spinal artery (ASA) and/or posterior spinal artery contributions. Some authors treat conus medullaris AVMs as separate entities, though the angioarcitecture is similar. Type 3 lesions are known as juvenile or metameric AVMs with both extradural and intradural involvement. The classic Cobb syndrome is limited to metameric-origin malformations involving the spinal cord, bone, and skin.
The spinal arteriovenous metameric syndrome (SAMS) describes all forms of metameric malformations, even if the AVM does not involve the spinal cord. Type 4 spinal AVMs, refer to ventrally-located perimedullary fistulae on the pial surface, within the subarachnoid space, primarily receiving arterial contributions from the ASA. These have been subcategorized into A, B, and C based on size and complexity; venous hypertension and an...