Background Spontaneous direct carotid-cavernous fistula(CCF)is relatively rare and few reports have been found in the literature.The aim of this paper was to report the clinical characteristics,imaging findings and curative effect of endovascular treatment for patients with spontaneous direct CCF.Methods We retrospectively analyzed the clinical data of nine patients with spontaneous direct CCF admitted between May 2003 and November 2007 and the outcomes of endovascular treatment.Sudden neuro-ophthalmological symptoms were the most common clinical presentation at diagnosis(n=8).No patients had a history of head trauma.Cerebral digital subtraction angiography(DSA)was performed on all cases under local anesthesia and seven cases received endovaSCUIar treatment.Results In eight patients,internal carotid angiograms recorded during the early arterial phase revealed aneurysms located in the cavernous sinuses,and in one patient,a dilated internal carotid artery(ICA)was seen.Among the nine cases,seven received endovascular treatment via a transarterial approach and complete occlusion of the fistula was obtained with no technique-related complications,one died suddenly before treatment and one gave up treatment.A detachable balloon was used as the embolic material in two cases.a detachable balloon and detachable coil as the embolic material in two cases,balloon-assisted coil embolization in two cases and covered stents were successfully placed in the parent vessel to exclude the aneurysm and fistula from circulation in one case.During a follow-up period of 3-48 months,all treated patients remained asymptomatic except for one patient who suffered from ipsilateral decreased vision.Conclusions Most spontaneous direct CCF may be caused by a ruptured intracavernous aneurysm with direct shunting into the cavernous sinus.Endovascular treatment seems to be a safe and effective method for treating spontaneous direct CCF.