Ophthalmology

Catherine A. Cox

Jordana F. Goren

A 68-year-old woman was transferred to Tufts Medical Center with worsening right-sided periorbital swelling and diplopia. She had previously been followed by an outside ophthalmologist for 1 month for presumed preseptal cellulitis.

History

The patient’s symptoms began 1 month before presentation as intermittent right-sided periorbital swelling and ptosis. She had been treated with various antibiotics for presumed cellulitis, including her current antibiotics of cefuroxime and metronidazole. Additional symptoms over the course of 1 month included an intermittent, subjective right-sided bruit as well as intermittent diplopia. The patient denied any history of trauma, headache, fever, chills or sinus pain. On the day of transfer to Tufts Medical Center, the patient presented to an outside hospital for worsening periorbital swelling and diplopia. She was found to have an IOP of 40 mm Hg in her right eye; therefore, she was started on oral acetazolamide plus brimonidine, latanoprost and timolol eye drops. A head CT was also obtained. The patient had no ocular history. Her medical history was significant for hypertension and hypothyroidism.

Examination

On examination, the patient’s visual acuity was 20/40 in the right eye and 20/20 in the left eye. Her right pupil was fixed at 5 mm, and her left pupil was reactive with no reverse afferent pupillary defect. IOP was 30 mm Hg in the right eye and 10 mm Hg in the left eye. Extraocular movements were restricted in the right eye and full in the left eye. Confrontation visual fields were full in both eyes. The patient was able to identify all Ishihara color plates with both eyes. Exophthalmometry showed 6 mm of right eye proptosis. Slit lamp biomicroscopy of the right eye revealed a swollen and ptotic lid (Figure 1), 360° of chemosis with prominent corkscrew vessels inferiorly (Figure 2), as well as corneal Descemet folds. The rest of the anterior segment and dilated fundus examinations were within normal limits in both eyes.

Figure 1. Significant right-sided periorbital edema and erythema. Ptosis and anisocoria are seen as well. Images: Vuong LN, Hedges TR

Figure 2. Right eye chemosis with inferior dilated corkscrew vessels.

What is your diagnosis?

Swelling, diplopia

Given the patient’s presentation, our first concern was for a carotid-cavernous fistula or dural shunt. Orbital cellulitis, including a subperiosteal abscess or cavernous sinus thrombosis, was also a possibility. Inflammatory processes including thyroid ophthalmopathy, idiopathic orbital pseudotumor, sarcoidosis or vasculitis were also considered. Finally, neoplasm was unlikely but still in our differential.

Review of the outside hospital CT scan revealed a dilated right superior ophthalmic vein and an enlarged cavernous sinus (Figure 3). These findings were consistent with a right-sided carotid-cavernous fistula. An MRI with angiogram confirmed our diagnosis by revealing branches of the internal carotid artery in communication with the cavernous sinus. No venous thrombosis of the cavernous sinus was present.

Discussion

Carotid-cavernous fistulas can be classified as one of two types: high-flow with direct communication between the internal carotid artery and cavernous sinus; or low-flow with indirect communication via arterial branches between the internal carotid artery and cavernous sinus. The latter is sometimes also referred to as a dural shunt. The Barrows classification further sorts dural shunt/carotid-cavernous fistulas by the specific internal carotid artery branches involved.

High-flow carotid-cavernous fistulas are commonly diagnosed in young men after significant head trauma. These types of fistulas may also be secondary to aneurysm rupture or collagen vascular disease (eg, fibromuscular dysplasia, Ehlers-Danlos or pseudoxanthoma elasticum), or they can be idiopathic. Conversely, dural shunts are more frequently diagnosed in older women with microscopic communications between dural arteries and venous sinuses. Dural shunts are also more common in patients with chronic hypertension.

Symptoms associated with high-flow carotid-cavernous fistulas include audible bruits, headaches, blurred vision, diplopia, ocular/orbital pain, proptosis, chemosis, injection and/or ophthalmoplegia. In some cases, critical findings may include venous stasis retinopathy, exposure keratopathy, glaucoma and/or central retinal artery occlusion. Dural shunts may present similarly, but findings are typically less severe.

The gold standard for diagnosing a carotid-cavernous fistula is digital subtraction angiography. Nonetheless, CT and MRI imaging are often the first tests to be obtained due to their relative availability. Although CT and MRI may assist in diagnosis, they do not provide the detail of angiography. Transcranial Doppler may also be obtained in order to examine flow patterns within a diagnosed fistula.

Treatment options vary depending on either the type of fistula or patient symptomatology. There is spontaneous closure of 20% to 60% of dural shunts; thus treatment options tend to be conservative for these patients. If significant visual changes are present, intervention is advised. Possible interventions include embolization with a balloon, platinum coil, polyvinyl alcohol particulates or liquid adhesive. More invasive procedures include packing of the cavernous sinus, as well as suturing, clipping or sealing the fistula with glue or fascia. Ligation of the internal carotid artery has been reported, but this carries a highly variable success rate of 30% to 100%. Finally, stereotactic radiosurgery may be performed, although response to treatment is often quite delayed.

Follow-up

Our patient was admitted to neurosurgery, continued on IOP-lowering medications and scheduled for surgery. Before surgery, her right eye vision worsened from 20/40 to 20/200, and ocular motility became even further restricted. At this time, she was noted to be in angle closure with complete shallowing of her right eye anterior chamber. Ultrasound biomicroscopy showed a ciliary-choroidal effusion with anterior rotation of the ciliary body (Figure 4). The patient subsequently underwent an emergent embolization/coiling procedure with the neurosurgical team. By postoperative day 4, her diplopia had resolved, and she was noted to have improved visual acuity, extraocular motility and deepening of the anterior chamber in her right eye. One month after treatment, the patient’s right eye visual acuity was 20/40, extraocular movements were full, exophthalmometry showed no proptosis, IOP was within normal limits on one aqueous suppressant eye drop, and no chemosis or episcleral vessels were present.

Figure 4. Ciliary-choroidal effusion with anterior rotation of the ciliary body and shallowing of the anterior chamber vessels.

Summary

Carotid-cavernous fistulas may be misdiagnosed as preseptal cellulitis, allergic conjunctivitis or infectious conjunctivitis. A dural shunt/carotid-cavernous fistula should be considered when cellulitis does not respond to appropriate antibiotic treatment and worsening of vision occurs accompanied by proptosis, chemosis, dilated episcleral vessels and/or ophthalmoplegia. Although angiography is the gold standard for diagnosing high- and low-flow fistulas, CT and MRI scans may help with the diagnosis if superior ophthalmic venous dilation is present. Although many dural shunts close spontaneously, patients with vision-threatening symptoms should be referred for emergent surgical intervention.

References:

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• Laurel N. Vuong, MD, and Thomas R. Hedges III, MD, can be reached at New England Eye Center, Tufts University School of Medicine, 800 Washington St., Box 450, Boston, MA 02111; 617-636-4219; fax: 617-636-4866; website: www.neec.com.

• Edited by Catherine A. Cox, MD, and Jordana F. Goren, MD, MS. Drs. Cox and Goren can be reached at New England Eye Center, Tufts University School of Medicine, 800 Washington St., Box 450, Boston, MA 02111; 617-636-4219; fax: 617-636-4866; website: www.neec.com.