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Dural arteriovenous fistula and carotid-cavernous fistula
The risk of a dural fistula is set by its venous drainage: drainage into a sinus only is relatively benign, but reflux into cortical veins raises the risk of haemorrhage and deficit and requires treatment; a carotid-cavernous fistula presents with a red, bulging eye and a bruit.
Why it matters in the exam
A dural fistula is a direct connection between dural arterial branches and a venous sinus, usually acquired after sinus thrombosis, trauma or surgery. In the transverse-sigmoid region it presents with pulsatile tinnitus — a 50-year-old woman with one-sided pulsatile tinnitus is a classic exam scenario. Borden classification: type 1 — drainage into the sinus in the normal direction; type 2 — into the sinus with cortical venous reflux; type 3 — directly into cortical veins. The Cognard classification is similar, and its type 5 describes drainage into perimedullary veins with myelopathy. Cortical drainage raises the risk of haemorrhage and venous infarction, so it is treated: transarterial or transvenous embolisation, surgical disconnection of the draining vein, or radiosurgery. The spinal dural fistula is the commonest spinal vascular malformation: an older man with progressive myelopathy that worsens on exertion, cord oedema with flow voids on the cord surface on MRI, and treatment — disconnection of the fistula.
A carotid-cavernous fistula (CCF) is classified by Barrow: type A — direct, between the internal carotid artery and the sinus, usually traumatic and high-flow; types B to D — indirect, from dural branches, usually spontaneous in an older woman and low-flow. Symptoms come from overload of the superior ophthalmic vein: a red eye with "corkscrew" vessels, chemosis, proptosis with a bruit audible over the eye, ocular nerve palsy (mainly nerve 6) and raised intraocular pressure. Urgent treatment is needed for visual loss, rising intraocular pressure and cortical venous drainage. Treatment is usually endovascular: in the direct type closure of the tear with coils or a balloon, and in the indirect type a venous route through the inferior petrosal sinus or the superior ophthalmic vein.
Key points
- Cortical drainage — haemorrhage risk — treat.
- Borden 1 relatively benign; 2 to 3 dangerous.
- Direct CCF — trauma, proptosis, chemosis, bruit.
- Nerve 6 is injured first in the cavernous sinus.
- Spinal fistula — progressive myelopathy in an older man.
Summary table
| Condition | Drainage or mechanism | Presentation | Treatment |
|---|---|---|---|
| Borden 1 | Into the sinus in the normal direction | Pulsatile tinnitus | Observation or symptom-driven treatment |
| Borden 2 to 3 | Reflux or direct drainage into cortical veins | Haemorrhage, deficit, venous dementia | Closure: embolisation, disconnection, radiosurgery |
| Spinal dural fistula | Perimedullary veins | Progressive myelopathy in an older man | Disconnection of the fistula |
| Direct CCF (Barrow A) | Internal carotid to sinus, trauma | Proptosis, chemosis, bruit, nerve 6 | Transarterial closure |
| Indirect CCF (Barrow B to D) | Dural branches, spontaneous | Chronic red eye | Transvenous route |
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Sources
- AHA/ASA Scientific Statement on cerebral dural arteriovenous fistulas, 2023 — Classification and treatment
- Borden and Cognard classifications of dural arteriovenous fistulas, 1995 — Venous drainage patterns
- Barrow classification of carotid-cavernous fistulas, 1985 — Direct and indirect fistulas
Sources are given for further reading; the text is written afresh and not copied from them.
Reviewed by the Examqo AI Professor · 2026-11-06. The text may contain errors; when in doubt, check the source.