Carotid-Cavernous Sinus Fistula

Redness, irritation, and diplopia developed over 2 to 3 weeks in a 55-year-old man's left eye (A). The injection worsened and was unresponsive to eye drops. Ptosis, mild proptosis, and elevated intraocular pressure developed. A bruit was auscultated over the affected eye.

Contrast-enhanced CT scans (B, C) demonstrated an enlarged, bulging, convex bordered, enhancing left cavernous sinus; mild left proptosis; and dilated left posterior ciliary and superior ophthalmic veins.

Drs Carol A. Lundin and Joel M. Schwartz of Irvington, NY, diagnosed an arteriovenous fistula-in this case either an internal carotid artery (ICA) cavernous sinus fistula or a dural sinus fistula. The distinction between the two depends on which arterial vessel is abnormally communicating with the cavernous sinus (ie, the larger intracavernous ICA or a smaller meningeal branch that supplies the dural walls of the cavernous sinus). The definitive diagnosis can be made with either conventional or magnetic resonance angiography (MRA).

Figure D, the collapsed image from a flow-sensitive two-dimensional time of flight MRA, depicts flowing blood in large intracerebral vessels as areas of high (white) signal. Extravasated blood is seen outside the lumen of the left intracavernous ICA (L); whereas in the right cavernous sinus, the blood is flowing within the intracavernous ICA (R). The basilar artery is seen in the center.

A carotid cavernous sinus fistula can be congenital, may occur after severe head trauma, or can develop spontaneously. Spontaneous development may be attributable to a ruptured intracavernous aneurysm.

This can be lifesaving, as morbidity and mortality from a ruptured aneurysm into the subarachnoid space is far worse than bleeding and fistula formation to the venous space of the cavernous sinus. A history of severe head trauma-with or without a confirmed diagnosis of skull base fracture-may be elicited. Arterial hypertension and atherosclerosis also predispose to carotid cavernous sinus fistula.

Dural sinus fistulas may close spontaneously. They involve less arteriovenous shunting and therefore cause fewer symptoms than ICA cavernous sinus fistulas. Because of their higher pressure/flow, the latter lesions often require embolization to prevent ischemic injury to the eye and complications of exposure from proptosis.

This patient underwent intravascular closure of the fistula. His condition improved dramatically within days of the procedure.