Vertebrovenous fistula

Vertebrovenous fistulas are uncommon arteriovenous fistulas between the vertebral artery and the adjacent vertebral venous plexus ¹. They can present with a variety of symptoms, including bruits and neurological symptoms and occur either spontaneously, typically in patients with connective tissue disorders, or as a result of trauma or medical intervention ^1,2.

Terminology

Strictly speaking, a vertebrovenous fistula, also sometimes referred to as a vertebral-vertebral fistula or vertebral arteriovenous fistula, should be an abnormal communication between the vertebral artery and/or one of its branches and the adjacent vertebral venous plexus without an intervening capillary bed ². These terms have, however, been used to describe fistulas receiving contribution from other regional arteries (e.g. ascending pharyngeal artery or branches of the carotid artery) or draining into regional veins (e.g. vertebral vein or internal jugular vein) ².

Epidemiology

The epidemiology of vertebrovenous fistulas depends on the etiology ¹.

• spontaneous

  • 2:1 female to male

  • associated with connective tissue disorders

  • typically younger adults (15 to 55 years of age)

• traumatic

  • 2:1 male to female

  • typically younger adults (20 to 50 years of age)

• iatrogenic

  • no gender predilection

  • older individuals (30 to 70 years of age)

Clinical presentation

A minority of diagnosed vertebrovenous fistulas are asymptomatic. When symptoms and signs are present they are variable, and include ¹:

• bruit (most common)

• headache, dizziness, pain

• neurological deficits

  • weakness

  • paresthesia

  • posterior fossa ischemia

• high output cardiac failure

Pathology

The underlying cause in spontaneous vertebrovenous fistulas is most commonly connective tissue disorders (e.g. neurofibromatosis type 1 (most common), fibromuscular dysplasia, Ehlers-Danlos disease) and in this setting most commonly occurs at the C1 level ¹.

In contrast, iatrogenic cases are more commonly lower down in the neck (C5 and C6 most common) as a result of surgery for degenerative change or vascular access ¹. This accounts for the older age of this group.

Traumatic causes do not have a predilection for any given level ¹.

Radiographic features

The primary findings of vertebrovenous fistulas reflect increased flow and arteriovenous shunting into the vertebral venous plexus.

A 2023 classification was proposed based upon flow rate and type of connection ².

• type A

  • high-flow

  • direct communication between vertebral artery and adjacent veins

  • type A+: same as type A but with feeders from other arteries

• type B

  • low-flow

  • indirect supply from muscular or dural branches of the vertebral artery

  • type B+: same as type B but with feeders from other arteries

CT and MRI

Cross-sectional imaging will demonstrate the usual features of an arteriovenous shunting lesion with enlarged feeding vessels and engorged vertebral venous plexus. Depending on how the study is performed, arterial shunting (e.g. early opacification of the venous plexus) may also be identified.

Angiography (DSA)

Digital subtraction angiography is ideal in fully evaluating these lesions and enables endovascular treatment ².

Treatment and prognosis

Treatment is primarily endovascular ^1,2. This can be achieved by sacrificing the vertebral artery, provided adequate collateral supply is present (contralateral vertebral artery, basilar and circle of Willis communications) or by directly occluding the feeding branches, while preserving the vertebral artery ^1,2. Occasionally a transvenous approach can be used ². Overall, there is a very high rate of successful occlusion ¹.

Potential complications include ischemic damage, if insufficient collateral supply is present or due to propagation of clot above occlusion to involve intracranial circulation, and hyperperfusion due to removal of the high-flow shunt ¹.