Unilateral Exophthalmos as the Initial Presentation of a Carotid-Cavernous Fistula: A Case Report

Abstract

Aims: The objective of this report is to describe a rare case of spontaneous carotid-cavernous fistula (CCF) in an elderly woman, highlighting the diagnostic challenges and the role of endovascular management in preventing vision-threatening complications. Case Presentation: A 77-year-old woman with no prior medical or surgical history presented with a one-month history of painful redness in the left eye and recurrent severe headaches. Ophthalmic examination revealed reduced visual acuity (<1/10), ptosis, limited abduction, episcleral vessel dilatation, and a poorly reactive mid-dilated pupil. Intraocular pressure and fundus were normal. Initial suspicion of giant cell arteritis was considered, but inflammatory markers were inconclusive. Brain MRI with angiographic sequences revealed arterialization and enlargement of the cavernous sinus, consistent with an indirect CCF. Digital subtraction angiography confirmed the diagnosis, and transvenous endovascular embolization with detachable coils was performed successfully. The postoperative course was favorable, with resolution of ocular redness and pain, progressive recovery of ocular motility, and improvement of visual acuity to 5/10 at three months. No recurrence was observed during six months of follow-up. Discussion: Spontaneous CCFs represent approximately 30% of cases and occur predominantly in elderly women. Their pathophysiology involves arteriovenous shunting with venous hypertension transmitted to the superior ophthalmic vein, leading to ocular congestion and potential optic nerve compromise. Clinical manifestations are highly variable, and low-flow indirect fistulas may present with nonspecific findings such as conjunctival injection, headache, and ophthalmoplegia, which can mimic giant cell arteritis or other orbital disorders. MRI may demonstrate indirect signs, but digital subtraction angiography remains the diagnostic gold standard and is essential for therapeutic planning. Endovascular embolization, particularly via the transvenous approach, is currently the treatment of choice, offering high occlusion rates and excellent functional outcomes. Early diagnosis and treatment are crucial to avoid irreversible complications such as secondary glaucoma, ischemic retinopathy, or optic neuropathy. Conclusion: Spontaneous carotid-cavernous fistulas are rare but potentially sight-threatening vascular lesions. Their atypical presentation may delay diagnosis, particularly in elderly patients. Recognition of episcleral vessel dilation as a clinical warning sign and timely neuroimaging are essential. Endovascular embolization remains the gold standard treatment, ensuring excellent anatomical results and favorable visual outcomes.