Spinal Dural AVF¶

Definition¶

A spinal dural arteriovenous fistula (dAVF) is an abnormal connection between a radiculomeningeal artery and a radicular vein within the dural sleeve of a nerve root. It is the most common spinal vascular malformation (60–80% of all spinal vascular malformations), typically affecting men over 50. The fistula causes reversal of venous drainage, leading to venous congestion of the spinal cord (congestive myelopathy) with progressive neurological deterioration.

Pathophysiology¶

The arterial blood from the fistula drains retrogradely into the perimedullary venous system, increasing venous pressure and reducing the arteriovenous pressure gradient across the cord. This causes venous congestion, cord edema, and progressive ischemia — a potentially reversible condition if treated early.

Imaging Findings¶

MRI¶

T2-weighted — Diffuse, centromedullary T2 hyperintensity extending over multiple segments (venous congestion edema), typically in the lower thoracic cord and conus
Flow voids — Serpiginous flow voids on the dorsal surface of the cord, representing dilated perimedullary veins. This is the most specific MRI finding.
Cord expansion — Mild, from edema
Post-contrast — Cord enhancement (breakdown of the blood-cord barrier) and enhancing serpiginous vessels on the cord surface
Conus involvement — Commonly affected due to the watershed vascular territory

Spinal Angiography¶

Identifies the fistula at the dural sleeve level (most commonly thoracolumbar, T6–L2)
Shows early filling of a draining vein from a radiculomeningeal artery
The draining vein ascends along the dorsal cord surface

MR Angiography¶

Can localize the fistula level non-invasively, guiding selective catheter angiography

Clinical Pearl

Spinal dural AVF is the great mimic — it can be misdiagnosed as transverse myelitis, MS, tumor, or degenerative myelopathy because of the diffuse cord T2 hyperintensity. The key clue is the presence of serpiginous flow voids on the dorsal cord surface. If you see a progressive myelopathy with diffuse cord edema and perimedullary flow voids, dural AVF must be excluded before attributing the findings to another diagnosis.

Management¶

Endovascular embolization — Glue embolization of the fistula via catheter angiography
Surgical disconnection — Laminectomy with ligation of the draining vein at the dural exit point
Both approaches are effective; surgical disconnection has lower recurrence rates
Neurological improvement is possible if treatment occurs before irreversible cord damage

Key Points¶

Most common spinal vascular malformation — older men, thoracolumbar level
Causes venous congestion myelopathy — progressive and potentially reversible
Flow voids on the dorsal cord surface on T2 MRI are the hallmark
Diffuse cord edema on T2 with perimedullary flow voids = dural AVF until proven otherwise
Spinal angiography confirms the diagnosis and guides treatment
Early treatment prevents irreversible cord damage

References¶

Krings T, Geibprasert S. Spinal dural arteriovenous fistulas. AJNR Am J Neuroradiol. 2009;30(4):639-648. https://pmc.ncbi.nlm.nih.gov/articles/PMC7051782/
Jeng Y, Chen DY, Hsu HL, Huang YL, Chen CJ, Tseng YC. Spinal dural arteriovenous fistula: imaging features and its mimics. Korean J Radiol. 2015;16(5):1119-1131. https://pmc.ncbi.nlm.nih.gov/articles/PMC4559784/
Maimon S, Luckman Y, Strauss I. Spinal dural arteriovenous fistula: a review. Adv Tech Stand Neurosurg. 2016;43:111-137. https://pubmed.ncbi.nlm.nih.gov/26508408/
Kelley M, April D, Bagert B, Milburn J, Steven A. Spinal dural arteriovenous fistula: the missing-piece sign. Ochsner J. 2022;22(1):10-14. https://pmc.ncbi.nlm.nih.gov/articles/PMC8929228/
Zyck S, De Jesus O, Gould GC. Dural arteriovenous fistula. In: StatPearls. Treasure Island (FL): StatPearls Publishing; updated 2023 Aug 23. https://www.ncbi.nlm.nih.gov/books/NBK532274/
Expert Panel on Neurological Imaging; Agarwal V, Shah LM, Parsons MS, et al. ACR Appropriateness Criteria® myelopathy: 2021 update. J Am Coll Radiol. 2021;18(5S):S73-S82. https://pubmed.ncbi.nlm.nih.gov/33958120/
Spinal dural arteriovenous fistula. Radiopaedia.org. https://radiopaedia.org/articles/spinal-dural-arteriovenous-fistula