Carotid Cavernous Fistula



Carotid-cavernous sinus fistula is an abnormal communication between the internal or external carotid arteries and the cavernous sinus. These lesions may be classified based on the following: etiology (traumatic vs spontaneous), velocity of blood flow (high vs low), and anatomy (direct vs dural, or internal carotid vs external carotid).


Carotid-cavernous sinus fistulae occur because of traumatic or spontaneous rents in the walls of the intracavernous internal carotid artery or its branches. This results in short-circuiting of the arterial blood into the venous system of the cavernous sinuses.[1]

Direct carotid-cavernous sinus fistulae, which represent 70-90% of all carotid-cavernous sinus fistulae in most series, are characterized by a direct connection between the intracavernous segment of the internal carotid artery and the cavernous sinus. These fistulae usually have high rates of arterial blood flow and most commonly are caused by a single traumatic tear in the arterial wall.

Dural carotid-cavernous sinus fistulae are characterized by a communication between the cavernous sinus and one or more meningeal branches of the internal carotid artery, external carotid artery, or both. These fistulae usually have low rates of arterial blood flow and almost always produce symptoms and signs spontaneously, without any antecedent trauma or manipulation. The lesions may represent congenital arteriovenous malformations, which develop spontaneously or in association with atherosclerosis, systemic hypertension, collagen vascular disease, pregnancy, and during or after childbirth.



United States





Nearly all patients with a direct carotid-cavernous sinus fistula experience progressive ocular complications if the fistula is left untreated. Increasing proptosis, conjunctival chemosis, and visual loss occur over months to years, with central retinal vein occlusion and secondary glaucoma representing the most severe ocular complications.

Several investigators have reported severe epistaxis and intracerebral hemorrhage, potentially fatal, in patients with traumatic carotid-cavernous sinus fistulae. Subarachnoid hemorrhage also may complicate the course of a traumatic carotid-cavernous sinus fistula. A 3% incidence of spontaneous intracerebral hemorrhage caused by carotid-cavernous sinus fistulae has been reported.

Visual loss, although less frequent than in patients with direct carotid-cavernous sinus fistulae, occurs in 20-30% of patients with dural carotid-cavernous sinus fistulae and may be due to secondary ischemic optic neuropathy, chorioretinal dysfunction, including central retinal vein occlusion, or uncontrolled glaucoma.






Imaging Studies

Other Tests

Medical Care

Surgical Care


Medication Summary

The goals of pharmacotherapy are to reduce morbidity and to prevent complications. Medications used to decrease aqueous production include beta-blockers, carbonic anhydrase inhibitors (topical or oral), and alpha2-agonists.

Timolol 0.25% or 0.5% (Timoptic, Timoptic XE, Blocadren)

Clinical Context:  May reduce elevated and normal IOP, with or without glaucoma by reducing production of aqueous humor or by outflow.

Levobunolol 0.25% or 0.5% (AKBeta, Betagan)

Clinical Context:  Nonselective beta-adrenergic blocking agent that lowers IOP by reducing aqueous humor production and possibly increases outflow of aqueous humor.

Metipranolol 0.3% (OptiPranolol)

Clinical Context:  Beta-adrenergic blocker that has little or no intrinsic sympathomimetic effects and membrane stabilizing activity. Has little local anesthetic activity. Reduces IOP by reducing production of aqueous humor.

Carteolol 1.0% (Ocupress)

Clinical Context:  Blocks beta1- and beta2-receptors and has mild intrinsic sympathomimetic effects.

Betaxolol ophthalmic (Betoptic, Kerlone)

Clinical Context:  Selectively blocks beta1-adrenergic receptors with little or no effect on beta2-receptors. Reduces IOP by reducing production of aqueous humor.

Class Summary

Decrease intraocular pressure (IOP) by reducing the aqueous production.

Dorzolamide 2% (Trusopt)

Clinical Context:  Used concomitantly with other topical ophthalmic drug products to lower IOP. If more than one ophthalmic drug is being used, administer the drugs at least 10 min apart. Reversibly inhibits carbonic anhydrase, reducing hydrogen ion secretion at renal tubule and increases renal excretion of sodium, potassium bicarbonate, and water to decrease production of aqueous humor.

Brinzolamide 1% (Azopt)

Clinical Context:  Catalyzes reversible reaction involving hydration of carbon dioxide and dehydration of carbonic acid. May use concomitantly with other topical ophthalmic drug products to lower IOP. If more than one topical ophthalmic drug is being used, administer drugs at least 10 min apart.

Acetazolamide (Diamox, Diamox Sequels)

Clinical Context:  Inhibits enzyme carbonic anhydrase, reducing rate of aqueous humor formation, which, in turn, reduces IOP. Used for adjunctive treatment of chronic simple (open-angle) glaucoma and secondary glaucoma and preoperatively in acute angle-closure glaucoma when delay of surgery desired to lower IOP.

Methazolamide (Neptazane)

Clinical Context:  Reduces aqueous humor formation by inhibiting enzyme carbonic anhydrase, which results in decreased IOP.

Class Summary

By slowing the formation of bicarbonate ions with subsequent reduction in sodium and fluid transport, it may inhibit CA in the ciliary processes of the eye. This effect decreases aqueous humor secretion, reducing IOP.

Brimonidine (Alphagan)

Clinical Context:  Selective alpha2 receptor that reduces aqueous humor formation and increases uveoscleral outflow.

Apraclonidine 0.5% or 1% (Iopidine)

Clinical Context:  Reduces elevated, as well as normal, IOP whether or not accompanied by glaucoma. A relatively selective alpha-adrenergic agonist that does not have significant local anesthetic activity. Has minimal cardiovascular effects.

Class Summary

The exact mechanism of ocular antihypertensive action is not established but appears to be a reduction of aqueous humor production.

Further Outpatient Care

Inpatient & Outpatient Medications



Ingrid U Scott, MD, MPH, Professor, Department of Ophthalmology and Public Health Sciences, Pennsylvania State University College of Medicine

Disclosure: Nothing to disclose.

Specialty Editors

Stephen D Plager, MD, FACS, Chief, Department of Ophthalmology, Dominican Hospital; Assistant Clinical Professor, Department of Ophthalmology, Stanford University Hospital

Disclosure: Nothing to disclose.

Simon K Law, MD, PharmD, Clinical Professor of Health Sciences, Department of Ophthalmology, Jules Stein Eye Institute, University of California, Los Angeles, David Geffen School of Medicine

Disclosure: Nothing to disclose.

Mark T Duffy, MD, PhD, Consulting Staff, Division of Oculoplastic, Orbito-facial, Lacrimal and Reconstructive Surgery, Green Bay Eye Clinic, BayCare Clinic; Medical Director, Advanced Cosmetic Solutions, A BayCare Clinic

Disclosure: Allergan - Botox Cosmetic Honoraria Speaking and teaching

Lance L Brown, OD, MD, Ophthalmologist, Affiliated With Freeman Hospital and St John's Hospital, Regional Eye Center, Joplin, Missouri

Disclosure: Nothing to disclose.

Chief Editor

Hampton Roy Sr, MD, Associate Clinical Professor, Department of Ophthalmology, University of Arkansas for Medical Sciences

Disclosure: Nothing to disclose.


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