Anterior Cranial Fossa Dural Arteriovenous Fistula Presenting as Subdural Hematoma
- Background:
- Anterior cranial fossa DAVFs are rare (5.8%) and have a high rate of sudden massive intracranial hemorrhage.
- Anterior cranial fossa DAVFs usually receive arterial blood supply from ethmoidal branches of the ophthalmic artery. As there is no dural sinus in this location, these fistulas drain directly into the frontal cortical veins (Borden type III).
- Different classifications of DAVFs have been developed; Borden and Cognard are the most commonly used.
- Clinical Presentation:
- Symptoms related to lesion location and pattern of venous drainage: pulsatile tinnitus, objective bruit, cranial nerve palsies, ocular symptoms including proptosis and chemosis (“red eye”), optic nerve atrophy, papilledema, headaches, nausea, vomiting, epileptic seizures, focal neurologic deficit, and intracranial hemorrhage
- The venous drainage pattern determines the severity of symptoms, depending on whether or not there is venous hypertension or cortical venous reflux.
- Key Diagnostic Features:
- Nonenhanced CT: The dilated veins and venous pouch can be seen as an extra-axial hyperdense mass, with a round shape and well-defined margins. Other complications such as intracranial hemorrhages and edema due to venous congestion can be noted.
- CT angiography: Enlarged arterialized veins and venous pouches usually are seen with early contrast opacification in an arterial phase. The dural branches supplying the fistula are also seen.
- MRI/MRA: Dilated cortical drainage veins and venous pouches can be detected as flow voids. An enlarged ophthalmic artery supplying the fistula can be seen.
- DSA (criterion standard): DSA remains the most accurate method for the detection and classification of DAVFs by determining the arterial supply and venous drainage.
- Differential Diagnoses:
- Extra-axial tumor: A DAVF can mimic a convexity meningioma. Meningioma usually shows hyperostosis of the underlying bone (while DAVF may show bone remodeling or erosion). On the other hand, a round shape and smooth contour should lead to the consideration of a vascular lesion.
- Thrombosed intracranial aneurysm: CT and/or MRA usually show an isolated arterial lesion with a filling defect due to intraluminal thrombus. Location is usually more proximal, although nonsacular aneurysms can be seen in distal branches.
- AVM: Findings are similar to DAVFs but the arterial supply depends on pial vessels and there is a nidus in the brain parenchyma.
- Treatment:
- Anterior cranial fossa DAVFs are usually treated with surgical disconnection.
- Endovascular therapy or, less commonly, radiosurgery can be considered if the surgical risk is too high.
