Ophthalmoplegia consistent with a pulse is one of the symptoms of direct carotid cavernous sinus fistula. A few direct carotid cavernous fistulas are spontaneous, mostly due to rupture of an aneurysm in the cavernous sinus segment of the internal carotid artery, and can be indistinguishable from traumatic on angiography. What causes direct carotid cavernous sinus fistula? In addition to trauma as the main causative factor, the causes of spontaneous carotid cavernous sinus fistula are: anomalous myofiber dysplasia of the arterial vessel wall and Ehlers-Danlos syndrome or elastic fiber pseudoxanthoma easily lead to spontaneous carotid cavernous sinus fistula, in patients with Ehlers-Danlos syndrome, collagen deficiency causes arterial tortuosity and increased vascular fragility, often making the diagnosis and treatment of the transarterial route difficult. Osteogenesis imperfecta also presents with increased vascular fragility, leading to spontaneous carotid cavernous sinus fistula. Cases of inflammatory syphilitic and fungal arteritis leading to spontaneous carotid cavernous sinus fistula have been reported in the literature. The diagnosis is not difficult in the presence of clinical manifestations such as pulsating proptosis, intracranial murmurs, conjunctival congestion and edema, rhinorrhea, and a history of head trauma, and is supported by cranial CT and MRI showing protrusion of the eye and thickening of the intraorbital ophthalmic vein or intracranial drainage vein and accompanying cerebral tissue edema, as well as TCD and SPECT. Internal carotid artery and vertebral artery angiography on both sides must be performed routinely, supplemented by external carotid artery angiography if necessary, to facilitate a clear diagnosis and a comprehensive understanding of the carotid cavernous sinus fistula blood supply and draining veins.