9 Carotid-Cavernous Fistulas
Abstract
Carotid-cavernous fistulas (CCFs) are rare, potentially life-threatening, conditions that often threaten vision. Their presentation and classification is central to the diagnosis and treatment of these lesions. As understanding of the pathology and natural history of CCFs progressed, new avenues of intervention developed and evolved. A number of neurointerventional techniques have been developed to safely and effectively treat these complex lesions.
Keywords: carotid-cavernous fistula, direct, indirect, dural, neurointerventional, endovascular, flow diversion, coil embolization, liquid embolics
9.1 Goals
1. Review clinical presentation of carotid-cavernous fistulas (CCFs) and discuss factors impacting diagnosis.
2. Review indications for treatment.
3. Review classification schemes and their role in determining treatment modality.
4. Critically analyze current and future treatment options.
9.2 Case Example
9.2.1 History of Present Illness
A 53-year-old Caucasian female presented to the neuro-oph-thalmology clinic for evaluation of retro-orbital pain, diplopia, and periorbital swelling following the sudden onset of left-sided headache 6 months prior. She complained of transient tingling in the left V2 distribution along with tinnitus. The symptoms were all exacerbated by strenuous exercise. She denied a history of trauma, seizures, or recent illnesses/infections. A computed tomography angiography (CTA) of the head revealed asymmetric enhancement of the cavernous sinus and a dilated left superior ophthalmic vein. She was referred to neurosurgery for evaluation.
Past medical history: Depression.
Past surgical history: None.
Family history: No known family history of vascular disorders or lesions.
Social history: 15 pack-year history. Weekly social use of alcohol and caffeine. No recreational drug use.
Review of systems: Positive for ringing in the left ear, transient diplopia, left eye swelling, and facial tingling.
Examination: Physical examination noted swollen and injected conjunctiva OS without proptosis. Her neurologic and physical examinations were otherwise normal and included a fundu-scopic examination and complete evaluation of extraocular muscles. Prior testing by neuro-ophthalmology also revealed no visual deficits and mildly asymmetric, but not elevated, intraocular pressure.
Imaging: The CTA demonstrated asymmetric avid enhancement of the left cavernous sinus (▶ Fig. 9.1a). In addition, a dilated superior ophthalmic vein was identified (▶ Fig. 9.1b) connecting with the angular vein (▶ Fig. 9.1c).
9.2.2 Treatment Plan
Due to the concerns for a CCF, arrangements were made for a digital subtraction angiogram (DSA). A six-vessel DSA was performed, and it demonstrated fistulous filling of the left cavernous sinus during (▶ Fig. 9.2a) selective left external carotid artery (ECA) injection, (▶ Fig. 9.2b) selective right internal carotid artery (ICA) injection, and (▶ Fig. 9.2c) selective left ICA injection. Venous outflow was via the superior ophthalmic vein to the angular and facial veins without evidence of retrograde cortical venous drainage.
Based upon the imaging findings, the recommendation was made for transvenous embolization of the fistula. The CCF was treated with transvenous coil embolization via the inferior petrosal sinus; coiling was directed from the confluence of the left superior ophthalmic vein and cavernous sinus in a retrograde manner to the posterior cavernous sinus. Complete obliteration of the CCF was achieved without complications.
Fig. 9.1CT angiogram demonstrating (a) axial views of asymmetric avid enhancement of the LEFT cavernous sinus, (b) dilated superior ophthalmic vein (asterisk) and multiplanar reconstruction demonstrating (c) the superior ophthalmic (asterisk) and the angular veins (white arrow).
Fig. 9.3 Selected angiographic images after coil embolization demonstrating no definitive filling of the left cavernous sinus from (a) left external carotid artery injection in the lateral projection, (b) left internal carotid artery injection in the lateral projection, and (c) native view of the coil mass in the lateral projection.
9.2.3 Follow-up
The patient remained neurologically intact and was discharged home on postoperative day 1 with resolution of all presenting symptoms. However, the patient returned on postoperative day 4 with a partial left abducens palsy. A CTA demonstrated near complete resolution of the previously dilated left superior ophthalmic vein. A repeat DSA demonstrated no fistulous connections to the cavernous sinus (▶ Fig. 9.3a, b) with a stable coil mass (▶ Fig. 9.3c). A follow-up angiogram 6 months postoperatively demonstrated continued obliteration of the fistulous connections. The partial abducens palsy had resolved.
9.3 Case Summary
1. How can this carotid-cavernous fistula be classified?
After the seminal 1985 publication,1 the Barrow classification became the most widely used scheme to describe CCFs. This classification system was based on angioarchitecture, and it categorized CCFs into four distinct types.
Type A direct CCFs have a direct connection between the cavernous ICA and the cavernous sinus usually due to a rupture in the carotid wall. These CCFs are high-flow lesions and have a low chance of resolving without intervention. The high-flow characteristics and their rapidly progressive nature make type A CCFs more likely to lead to vision loss.
Types B, C, and D are known as indirect or dural fistulas and arise from connections between the cavernous sinus and meningeal branches from the ICA (type B), meningeal branches from the ECA (type C), or both (type D). Type B, C, and D CCFs are less common than type A CCFs. For our patient, the imaging showed supply from bilateral internal and ipsilateral external carotid arteries (type D).
2. Which patient factors aid in determining conservative management versus treatment?
In 60 to 90% of cases, symptoms involve the orbit (conjunctival injection, chemosis, proptosis, glaucoma, diplopia, orbital hemorrhage, retro-orbital pain, and visual changes including vision loss). Less frequently, there can be progressive pain in the trigeminal distribution most commonly involving the V2 distribution. More rare presentations include intracranial hemorrhage, subarachnoid hemorrhage, epistaxis, or otorrhagia. CCFs can also present with headaches or tinnitus. While the decision to treat type A CCFs is straightforward, type B-D CCFs require more consideration given the greater likelihood of spontaneous resolution. While any threat to vision warrants treatment, patients with only headaches and/or tinnitus may require more nuanced discussions. In this instance, the patient had 6 months of intermittent diplopia, conjunctival injection, headaches, V2 sensory changes, and persistent tinnitus. She did not have hemorrhage, proptosis, elevated intraocular pressure, or vision changes; however, the symptoms were significantly impacting her quality of life. The treatment decision was elective and based on consideration of the risks, benefits, and alternatives.
3. How did both the type of fistula play a role in determining treatment modality?
There are multiple management options for CCFs: serial imaging, conservative treatment with manual external carotid compression, embolization, radiosurgery, and open surgery. However, endovascular treatment is the preferred treatment modality and includes the largest range of treatment options. Current endovascular modalities include detachable coils, liquid embolic agents (N-butyl cyanoacrylate [NBCA] and ethylene vinyl alcohol copolymer [EVOH]), covered stents, and flow diverting stents. Depending on the specific characteristics of the CCF, the lesion can be accessed via transvenous, transarterial, or combined approaches. Because this indirect CCF was fed from both ICA and ECA branches, we elected to proceed with transvenous coil embolization of the cavernous sinus.
4. What manner of follow-up is appropriate for these lesions? Cross-sectional imaging of all types is limited in the ability to detect fistulous connections. Therefore, a follow-up DSA should be performed to confirm successful treatment. There is no definitive recommendation for the timing of a follow-up study, but treatment modality and symptomatology can influence the time frame. However, the most common strategy described in the literature is a 6-month follow-up angiogram with the option for an additional 1-year follow-up angiogram.
9.4 Level of Evidence
The current level of evidence for endovascular treatment of CCF is Level C due to the lack of randomized controlled trials or other data to support a higher level. This is not unexpected, given the relative infrequency of presentation and the changing treatment modalities over the past several decades. There are a large number of studies indicating benefit of endovascular intervention. However, these studies are almost entirely composed of cohort studies, retrospective analyses, and case reports. So while the level of evidence is low, treatment recommendations can be considered strong (Class Ha) due to the amount of published data and the anticipated natural history of CCFs.
9.5 Landmark Papers
Surgeries for pulsating exophthalmos have been performed since the early 1800s. If conservative measures failed, surgeons often proceeded to ligation of the common or internal carotid artery. Treatment modalities changed with the introduction of detachable balloon catheters by Serbinenko in 1974.2 The papers below give an abbreviated history on the classification of CCFs and how treatments have evolved since the 1980s. Beyond these select articles, there are many additional papers that have significantly contributed to the body of knowledge.3,4,5
Barrow DL, Spector RH, Braun IF, et al. Classification and treatment of spontaneous carotid-cavernous sinus fistulas. J Neuro-surg. 1985;62:248-256}
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