Spinal arteriovenous malformations: a review with case illustrations

Spinal arteriovenous malformations are united by the existence of arteriovenous shunting but are quite heterogeneous in terms of pathology. Until recently, the pathological confusion has been such that management has been poorly understood and this is magnified by the rarity of the lesions. Type 1 AVMs, where the fistula is located in the dura, usually present with a venous hypertensive myelopathy and are relatively easily dealt with surgically. Type 2 AVMs, most closely mimicking the parenchymal AVMs of the brain, usually present with haemorrhage and may be surgically remediable but with much greater risk than the type 1 lesions. Type 3 AVMs, with a diffuse location through both the cord and extra-CNS tissue, usually present early in life with a myelopathy and are often untreatable. Type 4 AVMs, with a fistula located on the pial surface of the cord, usually present with a venous hypertensive myelopathy or subarachnoid haemorrhage, can be treated relatively easily by surgery when small but may be better treated endovascularly when the fistula is large. The purpose of this review is to summarise the current pathological, clinical and management literature with illustrative cases underscoring the important features of this heterogeneous disorder.