The Common Vein Copyright 2010
Carotid cavernous fistula is an abnormal communication between the carotid artery and the cavernous sinus.
It leads to increased venous pressure, decreased venous drainage and a thus decrease in blood pressure and perfusion. A direct and indirect are described.
Direct carotid cavernous fistula occurs when there is direct passage of arterial blood through an alteration of the internal carotid artery wall in its intracavernous portion. In indirect fistula, blood flows indirectly into the cavernous sinus through the meningeal branches of the internal or external carotid arteries.
They are usually caused either by trauma or spontaneous rupture of atherosclerotic artery or intracavernous aneurysm.
Clinically, patients have chemosis and congestion of episcleral and conjunctival blood vessels. There can be glaucoma secondary to increased episcleral pressure, or necrosis of the anterior segment. Proptosis, ophthalmoplegia can also develop.
Diagnosis is made through radiology, with CT and MRI being the preferred radiologic modalities, though MRI and angiography are superior in evaluating severity. Findings include enlargement of the cavernous sinuses, and the superior ophthalmic vein with tortuosity. Proptosis and engorgement of the extraocular muscles can also be detected.
Treatment is done in interventional radiology, with placement of intravenous spiral coils in the internal carotid artery.