Endovascular techniques for treatment of carotid-cavernous fistula

Carotid-cavernous fistulas (CCFs) are abnormal arteriovenous communications in the cavernous sinus. Direct CCFs result from a tear in the intracavernous carotid artery. Indirect CCFs generally occur spontaneously and cause more subtle signs. Direct CCFs, which typically have high flow, usually present with ocular-orbital venous congestive features and cephalic bruit. Indirect CCFs, which typically have low flow, present with similar but more muted clinical features. Direct CCFs are always treated with endovascular methods. The goal is to occlude the fistula but preserve the patency of the internal carotid artery (ICA). Agents include detachable coils or liquid embolic agents delivered transarterially or transvenously. Arterial porous or covered stents are often used adjunctively. In rare cases, the ICA must be occluded. Indirect CCFs are only treated if symptoms are intractable or intolerable or if vision is threatened. The goal is to interrupt the fistulous communications and decrease the pressure in the cavernous sinus. The traditional approach has been transarterial embolization with liquid agents, particularly n-butyl cyanoacrylate (n-BCA). However, the multiplicity of arterial feeders and the low success rate in occluding indirect CCFs by the arterial route has led to a preference for transvenous embolization, most commonly via the inferior petrosal sinus. If that sinus is impassable, alternative routes include the pterygoid venous plexus, superior petrosal sinus, facial vein, or ophthalmic veins. The cavernous sinus is occluded with coils, liquid embolic agents, or both. The use of ethylene vinyl alcohol copolymer (Onyx), an agent that may be superior to n-BCA because it may allow better distal fistula penetration. However, more safety and efficacy data must be accumulated. When experienced interventionalists are involved, the success rate for closing direct fistulas is 85%-99% and for closing indirect fistulas is 70%-78%. Serious complications are relatively infrequent.