Key-words:
Arteriovenous fistula - glue embolization - spinal vascular malformation
Introduction
Spinal Extradural arteriovenous (AV) fistula is rare vascular lesions and is defined as abnormal direct connection between the radicular artery or arteries and extradural venous plexus within the spinal canal and/or intervertebral foramen. They are divided into Type A and Type B depending on the presence or absence of intradural venous drainage, respectively. Because of the lesion's rarity the understanding of its natural history and treatment results is limited. The case and its management are thus presented for its rarity.
Discussion
Spinal extradural AVF is a rare distinct clinical entity which needs to be identified and differentiated from more common seen spinal dural AVF. Spinal epidural AVF is excluded from the most common classification scheme of spinal AV shunts.[[1]]
Spetzler et al.,[[2]] in his modified classification system of spinal vascular malformation categorized AVF into extradural and intradural AVFs. They are typically supplied by radicular artery and drains into epidural venous plexus. Based on the venous drainage Takai and Taniguchi,[[3]] classified it into Type A – epidural AVF with and Type B – epidural AVF without intradural venous drainage. Our present case is type B spinal epidural AVF.
Type B spinal epidural AVF are more common at the cervical level as in our case they are also associated with neurofibromatosis Type-1.
Takai and Taniguchi[[3]] in there literature review of spontaneous spinal epidural AVF analyzed 45 cases of spinal epidural AVF till 2011 out of which 23 were Type B.
These lesions are mostly symptomatic due to mass effect, occasionally due to hemorrhage. Recruitment of intradural veins and resultant venous hypertension can serve as a considerable source of morbidity.
Huang et al.[[4]] performed a pooled analysis of spinal epidural AVF in 2013 and identified 101 patients which also included post trauma and post spine surgery cases. In their analysis, 68% endovascular embolization while 32% underwent surgery. The obliteration rates were 87% for endovascular group and 92% for surgical group. These lesions require multiple session of embolization as there are multiple feeders, though in our case, we could achieve complete obliteration of the fistula in single session.
Following treatment, these patients showed marked improvement in clinical status, similar to what we observed in our case.
Asai et al.[[5]] reported a similar case where they used liquid embolic agent and coils to embolise the fistula which they surgically removed 1 week later. In 2015, Kasliwal et al.[[6]] had a similar case which was treated with endovascular method using coils and liquid embolic agent with stable results and clinical improvement.
To conclude, we reported a rare case of spinal epidural AVF with totally extradural venous drainage which was also causing intracranial venous hypertension. It was treated with endovascular embolization which remains the main stay of treatment in such cases following which excellent clinical recovery is expected. These cases need to be differentiated from other commonly encountered spinal AVF notably dural AVF. Complete obliteration should be target to avoid treatment failure or recurrence. The importance of understanding of vascular anatomy to avoid treatment failure and complications cannot be overemphasized.
Declaration of patient consent
The authors certify that they have obtained all appropriate patient consent forms. In the form, the legal guardian has given his consent for images and other clinical information to be reported in the journal. The guardian understands that names and initials will not be published and due efforts will be made to conceal identity, but anonymity cannot be guaranteed.
