Cavernous Sinus Arteriovenous Fistula

What is it?

Communication between arteries and veins in cavernous sinus that often shunts blood forward into eye and orbit under high pressure
Often called "carotid-cavernous fistula"
May occur after head trauma when intracavernous carotid artery is torn and develops hole ("direct" fistula)
May also occur spontaneously, mostly in postmenopausal or postpartum women and occasionally in men ("indirect" or "dural" fistula)
Causes unpleasant symptoms and sometimes irreversible visual loss
Diagnosis often delayed because this condition mistaken for other causes of red eye

Engorged radial conjunctival vessels that lead up to corneal limbus ("corkscrew vessels")
Swelling of lids
Proptosis (exophthalmos)
Double vision
Periocular pain
Reduced vision
Elevated intraocular pressure
Retinal vein engorgement
Patients may hear "whooshing" sound in one or both ears synchronous with pulse ("pulsatile tinnitus")

Viral and allergic conjunctivitis, but usually resolve within 14 days
Chronic conjunctivitis caused by autoimmune disease or chlamydia, but does not cause other features of fistula
Anterior uveitis, but causes photophobia and no other features of fistula
Scleritis, but usually causes focal conjunctival redness and more periocular pain than does fistula
Orbital cellulitis, but more common in children and immune-compromised adults
Idiopathic orbital inflammation, but orbital imaging should make distinction
Graves disease, but has lid retraction and lag
Orbital tumor, but orbital imaging should make distinction

CT or MRI often shows dilated superior ophthalmic vein, but...
Catheter angiography necessary to diagnose fistula, but...
Perform catheter angiography only if fistula requires endovascular closure
Indirect (dural) fistulas may eventually close spontaneously, but...
If symptoms are intolerable or vision is threatened, endovascular embolization must be performed, often requiring several procedures before closure is achieved and with risk of neurologic complications
Direct fistulas must be closed by endovascular embolization performed by interventional radiologist; success high but neurologic complications may occur