Cavernous sinus fistula, accurately called internal carotid cavernous sinus fistula, refers to the rupture of the internal carotid artery or a branch of the internal carotid artery and the entry of arterial blood into the cavernous sinus, causing an increase in pressure in the cavernous sinus, which results in a series of clinical manifestations. Most of the causes are due to trauma, and a few are spontaneous. The typical clinical manifestations are vascular murmur and pulsating proptosis, in which the patient feels a machine rumble-like murmur in the skull that intensifies with the pulsation of the artery. Due to the elevated pressure in the cavernous sinus and the impaired return of the ophthalmic veins, the patient’s eye will protrude outward and pulsate with the pulsation of the artery. The cavernous sinus fistula can be treated by surgically closing the fistula.