Perimedullary Arteriovenous Fistulae (PMAVF) are sometimes referred to as "direct" arteriovenous fistulae. They are similar in terms of their architecture to type 1 fistulae but the abnormal connection between vein and artery forms on the surface of the spinal cord itself, usually involving the anterior spinal arteries but occasionally one of the two dorsally situated posterior spinal arteries. These can be large and polyfistulous giving some difficulty distinguishing from an arteriovenous malformation on imaging.
This type of spinal vascular malformation may occur in children or in adults. It may occur in isolation or as part of another condition. For instance cases have rarely been reported in assosciation with Hereditary Haemorrhagic Teleangectasia. Disorders of the RASA1 pathway such as Capillary Malformation-Arteriovenous Malformation (CM-AVM) syndrome may also result in the development of PMAVF although they do not always produce symptoms.
The most common presentation in our experience is with malfunction of the spinal cord as a result of poor oxygen transfer to the neurones of the cord. There are also incidences of haemorrhage described usually from high-flow fistulae that develop areas of dilatation and weakness on the veins (venous ectasia).
The first line of therapy is usually endovascular embolisation which may be accomplished with liquid embolic agents (e.g.nCBA-glue, Onyx or similar) or coils. The point of fistulation will often be most safely and directly accessed through the tran-arterial route. If transarterial embolisation proves not to be feasible it is our experience that many PMAVF may be safely and effectively treated by microsurgical disconnection.