Unilateral, indirect spontaneous caroticocavernous fistula with bilateral abduction palsy.

Dear Editor,

Caroticocavernous fistulas (CCFs) are abnormal connections between the carotid artery and the cavernous sinus.[1] These lesions may be classified according to several criteria: angiographically, as direct or dural; pathogenetically, as spontaneous or traumatic; and hemodynamically, as high flow and low flow.[2] Angiographically, type A fistulas are direct shunts between the internal carotid artery (ICA) and cavernous sinus. Type B, C, and D are dural shunts. Type B fistulas are between meningeal branches of the ICA and cavernous sinus; type C fistulas are between meningeal branches of the external carotid artery (ECA) and cavernous sinus; andtype D fistulas are between meningeal branches of both ECA and ICA and cavernous sinus [Fig. 1].[2] Spontaneous CCFs are usually indirect and idiopathic; spontaneous closure is possible and mostly seen in women older than 50 years and hypertension is the most associated disease with fistulas.[13] CCFs can be unilateral or bilateral. A unilateral CCF can cause bilateral eye symptoms, whereas a bilateral CCF can present with unilateral eye symptoms. Signs like proptosis, chemosis, and nerve palsies are mostly seen at the side of the fistula.[4] This article reports bilateral abducens palsies with a unilateral spontaneous indirect CCF, which is very rare.

Figure 1

Angiographical classification of the carotid–cavernous fistula. ιnternal carotid artery; external carotid artery

A 76-year-old woman was admitted to our clinic with complaints of bilateral protruding eyes, redness, and inappropriate eye movements for 2 months. She had been treated at another hospital with intravenous and oral antibiotics and steroids, but symptoms and signs did not improve. There was no history of trauma. Ophthalmic examination showed corrected visual acuity of 20/50 (on Snellen's chart) in the right and 20/100 in the left eye. There was bilateral proptosis and abduction limitation. At the biomicroscopic examination, conjunctival hyperemia and chemosis were present. Blood in Schlemm's canal was observed on gonioscopic examination in both eyes [Fig. 2]. Intraocular pressure was 21 and 33 mmHg in the right and left eye, respectively, measured with a noncontact air puff tonometer (with dorzolamide HCl and timolol maleate fix combination). Fundus examination revealed widespread retinal hemorrhages and retinopathy of stasis [Fig. 2].

Figure 2

Clinical pictures of the patient. Right eye abduction failure (a); left eye abduction failure (b); dilatation and increased tortuosity of episcleral vessels (c); blood in the Schlemm's canal (d); retinal hemorrhage and engorged venous channels (e and f)

Brain diffusion magnetic resonance imaging (MRI) showed a bilaterally enlarged superior ophthalmic vein [Fig. 3] and brain-neck computed tomography (CT) venography demonstrated a bilateral superior ophthalmic vein with dolicoectatic appearance. There was arterial flow in colored Doppler imaging of the ophthalmic vein. Based on these results, angiography was performed and demonstrated an indirect fistula feeding from the left internal carotid artery to the left cavernous sinus and via the intercavernous plexus to the right cavernous sinus [Fig. 4].

Figure 3

Magnetic resonance imaging – brain axial T1 postgadolinium image showed bilaterally enlarged superior ophthalmic vein

Figure 4

Angiograms of the patient. Enlarged right superior ophthalmic vein (bold white arrow) (a); lateral left internal carotid artery angiogram demonstrating an indirect caroticocavernous fistula feeding from the left ICA to the left cavernous sinus (thin white arrow) with reflux into the superior ophthalmic vein (bold white arrow, b)

Transvenous CCF embolization was performed by neuroradiology, but failed.

In CCFs, isolated abduction failure without CT evidence of ocular muscle swelling is due to an abducens palsy, while a generalized ophthalmoplegia is caused by mechanical restriction from swollen ocular muscles.[5] There was no significant extraocular muscle swelling in our patient.

Bilateral abduction failure with CCF is rarely seen. Leonard et al. reported a patient with a unilateral direct CCF with bilateral abduction failure and swelling of extraocular muscles. In our case, there was bilateral abduction failure with a unilateral indirect CCF.

Proptosis, chemosis, dilated conjunctival veins, blood in Schlemm's canal, uncontrollable elevated intraocular pressure, and retinal hemorrhages are major symptoms and signs of CCFs.[45] In our case, all of the above-mentioned symptoms were present bilaterally, but were more evident on the left eye.

As seen in our case, diagnosis of CCFs should be considered with bilateral eye symptoms and bilateral nerve palsies.