Carotid-cavernous fistulae are abnormal connections between the carotid artery or its branches and a large vein (cavernous sinus) behind the eye. The cavernous sinus receives blood from the orbit, the pituitary gland, and the brain.
A carotid-cavernous fistula may be either direct (high-flow) or spontaneous (indirect/low-flow).
Direct carotid-cavernous sinus fistulae generally are associated with trauma, surgical manipulation or rupture of cavernous aneurysm.
Indirect carotid-cavernous fistulae (low-flow) occur more commonly in middle-aged to elderly. Indirect fistulae can form as a result of trauma, clotting of the sinus with subsequent reopening or most frequently without any obvious causative factor, spontaneous.
The symptoms include pulsating bulging of the eye, most commonly with a direct, high flow type, redness and swelling of the whites of the eyes, increased pressure in the eye (glaucoma), loss of vision in the eye (occurs in 20-30% of patients with indirect (low-flow) carotid-cavernous fistulae, and almost 100% of all direct (high flow) fistulae), double vision, and pain.
