A 62-year-old Caucasian female presented with spontaneous right-sided eye pain, chemosis and ophthalmoloplegia. A right carotid-cavernous sinus fistula was discovered and successfully treated with transvenous introduction of Guglielmi detachable coils. In addition to complete fistula occlusion, follow-up angiography 6 weeks post-treatment demonstrated the presence of a patent persistent trigeminal artery previously hidden by the caliber of the carotid-cavernous sinus fistula. The spontaneous nature of the presentation and the proximity of the persistent trigeminal artery to the site of coil embolization suggest spontaneous rupture of a persistent trigeminal artery aneurysm as cause of the fistula. Current literature on this finding is discussed here, demonstrating that an aneurysm of the persistent trigeminal artery leading to carotid-cavernous sinus fistula formation is rare. Furthermore, the present case is the first report of its kind in world ophthalmology literature.