Case history

A 17-year-old female was transferred to our hospital 4 days after being involved in a motor vehicle accident, in which she was the only survivor. She was diagnosed with a diffuse axonal injury, right femoral fracture, right peroneal nerve injury, left knee dislocation, mandible fractures, and diabetes insipidus. Ophthalmology was consulted for red eye with limited extraocular movements. Initial computed tomography scan of the orbits was reported as normal. She had no significant past medical or ophthalmic history.

Physical exam

On bedside exam in the ICU visual acuity could not reliably be assessed due to sedation. Subsequent evaluation revealed a Snellen visual acuity of 20/200 in the right eye and 20/30 in the left eye. Pupils were 1 mm bilaterally with afferent defect appreciated in the right eye. Intraocular pressures measured 25 mmHg in the right eye and 21 mmHg in the left eye with Tonopen tonometry. Extraocular movements were severely restricted in all gaze directions in the right eye and full in the left. Exophthalmometry showed 2 mm of proptosis on the right side. Anterior segment examination demonstrated engorged and tortuous vessels in the right eye with segmental subconjunctival hemorrhage. There was segmental subconjunctival hemorrhage in the left eye. Posterior examination revealed a cup to disc ratio of 0.2 bilaterally, normal vasculature and normal peripheral retina exam (Fig. 1).

Fig. 1
figure 1

a Engorged superior ophthalmic veins bilaterally. b Bilateral carotid cavernous sinus fistula with right being greater than left

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Discussion

Carotid cavernous fistula (CCF) is an abnormal vascular shunt from the carotid artery to the cavernous sinus. They are commonly classified based on hemodynamics, etiology or anatomically. Hemodynamic classification refers to whether the fistula is high or low flow. Etiology is commonly secondary to trauma or can occur spontaneously in the setting of aneurysm or medical conditions predisposing to arterial wall defects. Anatomic classification specifies whether the fistula is direct, arising from the carotid artery, or indirect; arising from one of the branches of the carotid artery.

There are four types of CCF based on Barrow’s classification system as seen in the paper by Ellis et al [1]. Type A is defined as direct high-flow lesion, often resulting from a single tear in the internal carotid artery wall. Type A CCF often result from trauma or may arise from an aneurysmal rupture and account for approximately 80% of CCF’s [1]. Type B CCF is low-flow indirect lesion arising from the meningeal branches of the internal carotid artery. Type C CCF arises from the meningeal branches of the external carotid artery. Type D is low flow and arises from the meningeal branches of both the internal and external carotid artery.

Trauma is the most common cause of CCF and accounts for up to 75–80% [1]. They predominantly occur in young males, who have a higher incidence of trauma. They are seen in up to 4% of patients who have sustained a basilar skull fracture [2]. CCF are thought to arise from either a direct tear from bony fracture or shear forces secondary to trauma. Spontaneous CCFs typically occur in older females as a result of ruptured internal carotid artery aneurysms or secondary to fibromuscular dysplasia, Ehlers-Danlos, and pseudoxanthoma elasticum [1].

Most common signs of CCF are dependent on whether the CCF is direct or indirect. Direct will commonly present rapidly with signs of chemosis (94%), proptosis (87%), increased intraocular pressure (60%), cranial nerve palsy (54%), diplopia (51%), and impaired vision (28%) [1, 4]. Orbital bruits, headache, and orbital pain may also be presenting features [1, 3]. Indirect CCF tends to present less dramatically with conjunctival injection often being the presenting sign, making diagnosis challenging. Cerebral angiography is the gold standard diagnostic modality. Non-contrast CT, MRI, or angiographic CT or MRI may also help to demonstrate the presence of a CCF [1].

First-line treatment consists of endovascular embolization with either a metallic coil, endovascular balloon or embolic agent. Complications include cerebral infarction, retroperitoneal hematoma, decreased visual acuity and ophthalmoplegia in up to 5% of patients [1]. In one series by Gupta et al., 88.8% of endovascular interventions for CCF were effective in curing the patient [5]. Surgical intervention may be considered in cases where endovascular treatment has been unsuccessful or is not possible. Success rates have been reported between 30 and 80% in the literature [1]. Radiosurgery appears to be effective in patients with indirect, low flow, CCF’s [5].

Bilateral CCFs are rare. A recent case report and literature review article of bilateral CCF found a total of 67 cases since 1954, 41 of which were post-traumatic [6]. All the cases with known patient details, had ocular involvement at initial presentation and were type A CCFs. Surgical ligation was employed more frequently in the earlier reported cases. However, it has mainly been replaced with transarterial endovascular embolization, which was first reported in 1987 [20]. An additional three cases were found on our search of literature that were not included in this recent review [28, 38, 40]. Table 1 summarizes all cases of post-traumatic bilateral CCFs with reported patient presentation, treatment and outcome.

Table 1 Summary of the reported cases of traumatic bilateral CCF
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In this case, ophthalmic consultation was sought for red eye with decreased eye movements. Ophthalmic exam revealed significant proptosis, chemosis, and elevated intraocular pressures, which in the setting of trauma suggested a possible CCF. Review of neuroimaging by the on-call ophthalmology resident confirmed the diagnosis of a bilateral CCF. The patient underwent endovascular embolization, which, was initially successful in treating her CCF. Unfortunately, she presented 1 month later with recurrent symptoms and endovascular intervention needed to be repeated. Second attempt at endovascular intervention was successful. Her visual acuity returned to 20/25 in the right eye and 20/20 in the left using Snellen visual acuity chart. Intraocular pressure returned to a normal range. Her afferent pupillary defect resolved. Her right eye had a persistent 6th nerve palsy throughout.

We were unable to determine if bilateral CCF’s vary in response to intervention compared to unilateral based on the literature available. In this case, two attempts at unilateral transarterial balloon on the most severely affected side were required to resolve the CCF.