The clinical presentation of carotid cavernous sinus fistula is closely related to the direction of the draining vein. Intracranial vascular murmurs and ocular symptoms are the most common, with ocular symptoms often being the first to appear and the primary reason for most patients to be seen. The causes of ocular manifestations are twofold: vascular factors and neurological factors. 1, intracranial vascular murmur: after the arterial blood flows into the cavernous sinus, it can drain into the subcavernous sinus or pterygoid plexus vein, and the abnormal blood flow forms a scour in this area, especially when the subcavernous sinus drains, it is more likely to appear intracranial murmur. Patients mostly report that they can hear intracranial murmurs consistent with arterial pulsations, blowing wind-like sounds, which are more obvious at night or during quiet time, making patients unbearable and irritable. Compression of the affected internal carotid artery may diminish or disappear the murmur. The size of the intracranial murmur is related to the size of the fistula, and the intensity of the murmur varies in the orbital, frontal, temporal, and postauricular regions due to the different directions of its venous drainage. The patient’s arterial blood enters the cavernous sinus after the rupture of the internal carotid artery or its branches, and because the ophthalmic vein has no valve, more than 90% of patients with carotid cavernous sinus fistula flow forward to the ophthalmic vein through the cavernous sinus, causing obstruction of ophthalmic venous reflux and congestion, resulting in a pulsating protrusion on the affected side. 90% of patients have a protruding eye, and the degree of protrusion is related to the duration of the fistula, and the direction of protrusion The direction of protrusion is usually axial and to a lesser extent downward, which is associated with congestion of the superior ophthalmic vein and its branches. If the intercavernous sinus is well developed, arterial blood from one side can drain into the bilateral cavernous sinus and ophthalmic veins, causing bilateral pulsating proptosis. 3. Bulbar conjunctival congestion and edema: In most cases, it is due to abnormal drainage of blood from the cavernous sinus to the orbit through the superior or inferior ophthalmic vein and poor blood return to the orbital tissues causing bulbar conjunctival ectropion in severe cases. Bulbar conjunctival congestion and edema is the most common clinical manifestation, and almost 100% of patients have different degrees of bulbar conjunctival edema. Ocular motility disorders: Due to the special anatomical relationship between the III, IV and VI cerebral nerves that govern eye movements and the cavernous sinus, patients with carotid cavernous sinus fistula may suffer from paralysis of the corresponding cerebral nerves due to factors such as enlargement of the cavernous sinus and elevated sinus pressure, resulting in ocular motility disorders. The abducens nerve is the most commonly involved, followed by the motoneurone nerve. The main symptoms are ptosis, diplopia, pupil dilatation, and limited eye movement. 5, neurological dysfunction: Simple carotid cavernous sinus fistula usually does not cause neurological dysfunction, but if there is severe “blood theft” with side branch development or poor compensation, it may cause insufficient blood perfusion to normal brain tissue, and symptoms of neurological dysfunction may occur. 6, vision loss: carotid cavernous sinus fistula patients can also cause visual impairment, due to obstruction of ocular venous reflux, bruising, increased venous pressure and inadequate blood supply to the ophthalmic arteries, resulting in retinal and optic disc edema, hemorrhage, secondary glaucoma, vision loss, and even blindness. Some patients do not have collateral circulation such as facial veins, resulting in a sharp increase in intraocular pressure and severe headache, which can lead to loss of vision in a short period of time. The incidence of blindness in patients with carotid cavernous sinus fistula has been reported in the literature to be about 3.1%. Other: When a carotid cavernous sinus fistula is accompanied by a skull base fracture or pseudoaneurysm, it can break into the pterygoid or septal sinus and cause fatal rhinorrhea. A few patients may also develop psychiatric symptoms, convulsions and hemiparesis, aphasia, etc.; when draining into the posterior cranial fossa, it may cause cerebellar and brainstem congestion and edema with corresponding neurological dysfunction.