Atypical Acute and Non-traumatic Presentation of an Indirect Carotid-Cavernous Fistula.

A carotid-cavernous fistula (CCF) is an abnormal communication between the carotid artery and the cavernous sinus. Contrary to the typical insidious onset, we present a case of an indirect CCF in a 49-year-old woman who presented with the sudden onset of a painful, swollen, and red left eye, which was initially misdiagnosed as orbital cellulitis. It is crucial to maintain a high index of suspicion in all patients who present with the sudden onset of ocular symptoms, particularly if they exhibit pulsatile proptosis, chemosis with arterialized conjunctival veins, periorbital bruit, elevated intraocular pressure (IOP), and normal inflammatory markers. Early diagnosis is essential to prevent vision loss and other associated neurological complications. The patient underwent transvenous coil occlusion of the left cavernous sinus but later developed a recurrent fistula, underscoring the need for close follow-up after endovascular intervention to detect any residual or recurrent fistula.