Low-flow carotid cavernous fistula
D. Magnetic resonance imaging with magnetic resonance angiography or digital subtraction angiography
Carotid cavernous fistula (CCF) is an abnormal communication between the carotid artery and its branches and the cavernous sinus (CS), causing high-pressure arterial blood flow within the low-pressure veins, sinuses, and cavernous sinus.1 Direct CCF (high-flow fistula) is a direct connection between the intracavernous segment of the internal carotid artery and CS, commonly caused by head injury. Presentations include blurred vision, pulsatile proptosis, orbital bruit, chemosis, corkscrew conjunctival vessels, raised intraocular pressure, and nerve palsies.1,2
Indirect CCF (low-flow fistula) involves 1 or more meningeal branches of the internal carotid artery, external carotid artery, or both, communicating with CS. It can be spontaneous, associated with hypertension, older age, and female gender. Often asymptomatic, the most common presentation is conjunctival congestion misdiagnosed as conjunctivitis.1,3 This patient had corkscrew vessels with serous choroidal detachment (CD) and normal intraocular pressure.4,5 This may occur due to increased orbital venous pressure and intracapillary pressure in the choroid, resulting in transudation into the suprachoroidal space.5