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Type 1 Vascular Malformation (dAVF)


KEY FACTS

Terminology

  • Synonyms: Type 1 spinal arteriovenous fistula (AVF), dural AVF, dural fistula

  • Definition: Spinal AVF, present within dura, with intradural distended draining veins

Imaging

  • Cord enlarged, T2WI hyperintense, vessel flow voids on cord surface

  • Multiple enhancing serpentine veins on cord surface

  • Dynamic contrast-enhanced MRA capable of defining dilated intradural veins; very useful to guide catheter angiography

  • Spinal catheter arteriography is gold standard for confirming diagnosis/treatment

Top Differential Diagnoses

  • Cerebrospinal fluid pulsatile flow artifact

  • Spinal cord tumor

  • Spinal cord arteriovenous malformation

  • Tortuous “redundant” roots from spinal stenosis

Pathology

  • Venous hypertension from engorgement reduces intramedullary AV pressure gradient, causing reduced tissue perfusion and cord ischemia

Clinical Issues

  • Most common presentation is progressive lower extremity weakness with both upper + lower motor neuron involvement

  • Very rarely presents with subarachnoid hemorrhage

  • Middle-aged man with progressive lower extremity weakness exacerbated by exercise

  • Persistent edema and enhancement of cord can occur even with successful clinical treatment of fistula

Sagittal oblique graphic of the thoracic cord shows site of a type 1 dural fistula at the dural root sleeve level
, with secondary dilatation of intradural venous plexus due to arteriovenous shunt.

Sagittal T2WI MR shows central cord T2 hyperintensity (edema) related to venous hypertension from the peripheral fistula shunting, which typically spares the cord periphery. There are multiple serpentine intradural flow voids from the arterialized and distended venous plexus
.

Sagittal T1WI C+ FS MR shows ill-defined diffuse enhancement of the distal thoracic cord
in this case of type 1 dural fistula. Faint to moderate cord parenchymal enhancement is common with this lesion.

Coronal reformat of double-dose dynamic enhanced spinal MRA shows the dilated coronal venous plexus throughout the thoracic spine
.

TERMINOLOGY

Synonyms

  • Type 1 spinal AVF, dural AVF (dAVF)

  • Dural fistula; type 1 spinal vascular malformation; radiculomeningeal fistula

Definitions

  • Spinal arteriovenous (AV) fistula, present within dura, with intradural distended draining veins

IMAGING

General Features

  • Best diagnostic clue

    • Abnormally enlarged, T2WI hyperintense distal cord covered with dilated pial vein flow voids

  • Location

    • Intradural extramedullary flow voids from distended draining veins

    • Variable, from upper thoracic to sacrum

      • –

        Most commonly occur at level of conus

  • Size

    • Variable

  • Morphology

    • Serpentine vessels on cord surface

CT Findings

  • CECT

    • Slightly enlarged distal spinal cord

    • Enhancing pial veins on cord surface

    • Much more difficult to diagnose on routine CT than MR imaging

  • CTA

    • Nidus in neural foramen shows focal enhancement, with prominent intradural draining dilated veins

    • Post-processing with multiplanar reformats mandatory

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