They are classified into 4 grades:
I) dural arteriovenous fistula, the most common lesion (%-80%), II) intramedullary arteriovenous malformation, whose nidus is located in the medullary parenchyma, fed by the anterior spinal artery anterior to the spinal cord, III) intramedullary arteriovenous malformation with extramedullary extension, whose feeder axes come from the vertebral plexuses, and finally IV) intradural permedullary fistula fed by the anterior spinal artery and draining directly into a permedullary vein (20%).
Their frequency is much rarer than that of cerebrovascular malformations, with an estimated incidence of between 2 and 11% of all cerebro-spinal arteriovenous malformations.
These spinal malformations are revealed by progressive symptoms, such as gait and/or sphincter disorders (myelopathy) or atypical sciatica (radicular syndrome).
While surgery is effective and relatively straightforward for the treatment of spinal dural fistulas, the treatment of AVMs is more complex, often requiring one or more embolization procedures. Radiosurgery is also a therapeutic option that may be discussed depending on the operative risks involved, or in the case of small malformative residues that are difficult to access using other modalities.