Figure 1. Initial presentation, right eye. Top left: External photograph of dilated, tortuous episcleral vessels. Above: Fundus photograph showing dilated, tortuous retinal veins with retinal hemorrhage and macular edema, confirmed by optical coherence tomography, left.
Diagnosis, Workup and Treatment

The combination of proptosis, central retinal vein occlusion, corkscrew episcleral vessels and elevated intraocular pressure raised concern for obstruction or arterialization of the orbital venous system, with carotid-cavernous sinus fistula being high on the differential diagnosis.

The patient’s records were obtained and reviewed. An MRI and MRA were performed during her recent hospitalization, which showed an apparent left enophthalmos with atrophy of the extraocular muscles, and was read as negative for mass, cavernous sinus thrombosis and arteriovenous malformation (AVM). The patient was subsequently referred to the Neuro-Ophthalmology Service at Wills Eye, where orbital Doppler imaging was performed. This showed non-arterialized reversal of flow in the right superior ophthalmic vein (SOV) and absence of flow in the right central retinal vein. Although she lacked the arterialized reversal of flow in the SOV reported in dural AVM, it was felt that she had entered the resolution phase, now at five months after her initial symptoms began.

She was seen by the Retina Service twice prior to her neuro-ophthalmology appointment, given intravitreal bevacizumab at each visit, and had notable improvement of the episcleral engorgement (See Figure 2a), retinal hemorrhages (See Figure 2b) and macular edema (See Figure 2c). Intraocular pressure declined to 12 mmHg in the right eye and vision improved to 20/60. Given her clinical improvement and following extensive discussion with the patient regarding the risks and benefits of conventional angiography, close observation with deferral of further imaging was elected.


Figure 2. Two and a half month follow-up, right eye. Above: External photograph of partial resolution of episcleral vessel dilation and tortuosity. Top right: Fundus photograph showing nearly resolved hemorrhage. Right: Optical coherence tomography showing minimal residual macular edema.
The patient presented with decreased vision secondary to central retinal vein occlusion, along with a questionable diagnosis of scleritis. While both scleritis1 and CRVO2 may be caused by vasculitic processes, their coexistence is rare, and generally found with posterior scleritis.3-7 The lack of history of trauma, negative findings on magnetic resonance angiography and sub-acute presentation made a high-flow carotid-cavernous fistula (CCF) unlikely.

CCF are classified as either direct (high flow) or indirect (low flow), with the latter arising from dural branches of the internal and external carotid arteries.8 High-flow CCF are most often caused by trauma and exhibit the classic pulsating exophthalmos with an orbital bruit. Conversely, low-flow CCF, also called dural arteriovenous malformations (DAVM), are postulated to occur via localized thrombotic events, with less dramatic presentation.8 Doppler ultrasound in DAVM classically shows arterialized reversal of flow in the SOV.9,10

DAVM most commonly present in females over 50 years old with hypertension, exhibiting exam findings of limbal vascular loops in 25 percent, venous stasis retinopathy via central retinal vein thrombosis in 15 percent and occasionally an orbital bruit.8 Magnetic resonance or CT angiography may be negative, with definitive diagnosis confirmed by super-selective conventional angiography. Angiography with endovascular treatment however, entails a 2 to 4 percent risk of stroke, vision loss, or other permanent neurologic morbidity.11,12 Many DAVM will spontaneously resolve, and the decision to pursue conventional angiography must weigh the risks and benefits of the procedure.

DAVM can cause significant ocular morbidity. The most serious complications are from intracerebral hemorrhage with resulting stroke, occurring in 3 percent of patients.13 These complications occur with deeper venous drainage of the fistula, and attempts have been made to clinically predict the patients who have such drainage patterns. Exam findings predictive of cortical venous drainage include bilateral orbital congestion, post-auricular bruit and CNS dysfunction.14

Indications for intervention in DAVM include progressive visual decline, ocular pain, glaucoma, ophthalmoplegia, proptosis and intracranial bleeding.8 Our patient did not have an indication for intervention, and was showing clinical improvement. After extensive discussion, a plan of close observation was agreed upon. Should she fail to improve further or develop an indication for intervention, treatment options include surgery, trans-arterial or trans-venous embolization and radiosurgery, with the latter two having reported success rates of 90 percent and significantly less morbidity than surgery.12,15  REVIEW

The author would like to thank John Pitcher, MD, of the Retina Service and Jennifer Hall, MD, and Mark Moster, MD, of the Neuro-Ophthalmology Service at Wills Eye Institute.  

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