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

Background

Carotid cavernous fistulas (CCFs) are abnormal connections between the carotid arteries and the cavernous sinus. CCFs often present with double vision, reduced visual acuity, and conjunctivitis. Deteriorating ocular symptoms caused by abnormal fistula drainage can cause permanent blindness, and so urgent interventional treatment is necessary. Transvenous embolization of the fistula is the primary treatment option for most patients with symptomatic CCFs. Orbital approaches are considered to be risky compared with the traditional approach via the inferior petrosal sinus and are thus used as a secondary option. These approaches include embolization via the superior ophthalmic vein, inferior ophthalmic vein, and medial ophthalmic vein and direct transorbital puncture. This study aims to assess the merits and risks of orbital approaches in transvenous embolization of CCFs.

Methods

A systematic review of 30 studies assessing the radiographic and clinical outcomes of this approach was conducted. Outcomes of interest included successful fistula closure, postoperative improvement of ocular symptoms, and complications from the procedure. Weighted averages were calculated for all outcomes.

Results

Transvenous embolization via an orbital approach had a high success rate (89.9%). Improvement in visual acuity and proptosis was found in 93.4% and 88.1% of patients, respectively. There were no major complications. Minor complications found included subconjunctival hemorrhage (n = 4), intraorbital hemorrhage (n = 1), eyelid hematoma (n = 1), and foreign-body granuloma (n = 3).

Conclusions

All orbital approaches for transvenous embolization of CCFs are effective and safe.

Introduction

Carotid cavernous fistulas (CCFs) are abnormal connections between the carotid arteries and the cavernous sinus. CCFs can be classified as 2 main subtypes, either direct high-flow CCFs or indirect low-flow CCFs.¹ Direct CCFs result from defects in the wall of the intracavernous carotid artery, which causes it to be in direct communication with the surrounding cavernous sinus.¹ This type of CCF often occurs as a result of trauma to the head and is most common in young men.² Indirect CCFs, also called dural arteriovenous fistulas, are pathologic connections between the cavernous sinus and the branches of the carotid arteries within the dura mater. The presentation of this subtype of CCF is seen more commonly in postmenopausal women.3, 4 Nevertheless, all types of CCFs result in increased blood flow and pressure within the cavernous sinus, typically resulting in fistulous flow draining into the orbital veins. The characteristic symptoms of this condition include reduced visual acuity, proptosis, chemosis, diplopia, and increased intraocular pressure.

Although some indirect CCFs can close spontaneously with conservative management, many cases of CCFs require interventional treatment to close the fistula.⁵ Endovascular treatments are most common and involve using an arterial or venous approach to reach the fistula. Embolization of the fistula can then be achieved by using a variety of substances such as platinum coils, Guglielmi detachable coils, detachable balloons, and liquid adhesives. In direct CCFs, a transarterial route is preferred; however, the small, tortuous arterial branches in indirect CCFs make this approach difficult. Therefore, transvenous embolization is typically used as a first option for treating all indirect CCFs or direct CCFs that have failed to resolve after transarterial embolization. Conventionally, transvenous embolization is achieved by an approach through the inferior petrosal sinus (IPS). However, when the IPS cannot be angiographically visualized or has thrombosed, alternative approaches via transorbital pathways have been used.

Embolization of the CCFs via the superior ophthalmic vein (SOV), inferior ophthalmic vein (IOV), and medial ophthalmic vein (MOV) has been successful in a variety of studies. Direct transorbital puncture into the cavernous sinus has also been implemented in some cases. Although an orbital approach is a direct and efficient way of accessing the cavernous sinus, it is not initially preferred, because studies have suggested that it may be more risky and elicit more complications than the traditional transfemoral approach through the IPS.⁶ Thus, to assess the merits and risks of an orbital approach, a systematic review was performed to investigate the clinical outcomes of transvenous embolization via an orbital approach for patients with CCF.