Orbital Approaches for Treatment of Carotid Cavernous Fistulas: A Systematic Review

An anatomical-angiographic classification for carotid-cavernous sinus fistulas is introduced and a series of 14 patients with spontaneous carotid-cavernous sinus fistulas is reviewed to illustrate the usefulness of such a classification for patient evaluation and treatment. Fistulas are divided into four types: Type A are direct high-flow shunts between the internal carotid artery and the cavernous sinus; Type B are dural shunts between meningeal branches of the internal carotid artery and the cavernous sinus; Type C are dural shunts between meningeal branches of the external carotid artery and the cavernous sinus; and Type D are dural shunts between meningeal branches of both the internal and external carotid arteries and the cavernous sinus. The anatomy, clinical manifestations, angiographic evaluation, indications for therapy, and therapeutic options for spontaneous carotid-cavernous sinus fistulas are discussed.

The author investigated 101 cases with direct dural carotid-cavernous and orbital arteriovenous fistulas (CCF). The characteristic clinical findings, such as specific epibulbar arterialized loops, are described and the differential diagnosis of the striking diagnostic triad (exophthalmos, the above-mentioned loops and glaucoma) is discussed, together with the exclusion criteria for other causes of red eyes, episcleral measurements and blood flow. The results of various diagnostic procedures, such as ultrasonography, Doppler hematotachography and color Doppler of the orbit and carotid systems, magnetic resonance imaging and angiography, and of conservative treatment and embolization processes are dealt with successively. The classification of different types of carotid-cavernous fistulas is presented,(1-3) together with the clinical signs in relation to morbidity and mortality during or after conservative or intervention therapies. The importance of patient follow-up, in the clinic as well as with Doppler methods, is emphasized in order to differentiate a progressive or diminished clinical condition caused by spontaneous thrombosis in the healing process or more arteriovenous flow. A 'decision tree' for use in daily practice is provided. In this study, of the 101 cases in which the localization was diagnosed by angiography, 42 were direct (30 traumatic, 12 spontaneous), 31 were dural (3 traumatic, 28 spontaneous) and 10 were orbital CCFs. In 18 other cases, usually dural or orbital shunts, angiography was not performed. For the management of 42 direct fistulas, conservative treatment was used in 12 cases (7 with success; 58%) and balloon embolization was performed in 18 cases (17 with success; 94.5%); the other cases were treated by direct or indirect surgery. Of the 48 (spontaneous and traumatic) dural fistulas, 39 were treated conservatively (32 recovered or were much improved: 82%, of the total cases, 67%). All seven cases in which embolization was performed were cured and/or much improved. In two cases, one fistula was conservatively treated while one was embolized at another location, both with success. Of the 10 orbital arteriovenous shunts showing signs of dural fistulas, the features disappeared in 8 cases, although after a much longer follow-up period than for the typical dural carotid-cavernous sinus fistulas; in one patient, direct surgery was performed successfully and in one patient the original, non-progressive, orbital features could still be observed.

Carotid cavernous fistula (CCF) is an abnormal communication between the cavernous sinus and the carotid arterial system. A CCF can be due to a direct connection between the cavernous segment of the internal carotid artery and the cavernous sinus, or a communication between the cavernous sinus, and one or more meningeal branches of the internal carotid artery, external carotid artery or both. These fistulas may be divided into spontaneous or traumatic in relation to cause and direct or dural in relation to angiographic findings. The dural fistulas usually have low rates of arterial blood flow and may be difficult to diagnose without angiography. Patients with CCF may initially present to an ophthalmologist with decreased vision, conjunctival chemosis, external ophthalmoplegia and proptosis. Patients with CCF may have predisposing causes, which need to be elicited. Radiological features may be helpful in confirming the diagnosis and determining possible intervention. Patients with any associated visual impairment or ocular conditions, such as glaucoma, need to be identified and treated. Based on patient's signs and symptoms, timely intervention is mandatory to prevent morbidity or mortality. The conventional treatments include carotid ligation and embolization, with minimal significant morbidity or mortality. Ophthalmologist may be the first physician to encounter a patient with clinical manifestations of CCF, and this review article should help in understanding the clinical features of CCF, current diagnostic approach, usefulness of the available imaging modalities, possible modes of treatment and expected outcome.