Vascular malformations of the spine and spinal cord* : anatomy, classification, treatment.

Spinal vascular malformations are rare diseases with a wide variety of neurologic presentations. Their classification depends on the differentiation of shunting versus nonshunting lesions, the latter being the spinal cord cavernomas. In the shunting lesions, the next step in the proposed classification scheme is related to the feeding artery which can subdivide the dural vascular shunts from the pial vascular malformations: while those shunts that are fed by radiculomeningeal arteries (i.e., the counterparts of meningeal arteries in the brain) constitute the dural arteriovenous fistulas, the shunts that are fed by arteries that would normally supply the spinal cord (i.e., the radiculomedullary and radiculopial arteries) are the pial cord arteriovenous malformations (AVMs; whose cranial counterparts are the brain AVMs). Depending on the type of transition between artery and vein, the latter pial AVMs can be further subdivided into glomerular (plexiform or nidus-type) AVMs with a network of intervening vessels in between the artery and vein and the fistulous pial AVMs. The last step in the classification then describes whether the type of fistula has a high or a low shunting volume which will differentiate the "macro-" from the "micro"fistulas. The proposed classification is therefore based on a stepwise analysis of the shunt including its arterial anatomy, its nidus architecture and its flow-volume evaluation. The major advantage of this approach is that it leads to a subclassification with direct implications on the choice of treatment, thereby constituting a simple and practical approach to evaluate these rare diseases.