Ophthalmoplegia consistent with a pulse is one of the symptoms of direct carotid cavernous sinus fistula. Direct carotid cavernous sinus fistulas are most often due to trauma. A few direct carotid cavernous sinus 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 are the tests for direct carotid cavernous sinus fistula? Cerebral angiography Cerebral angiography is mainly to understand the location and size of direct carotid cavernous sinus fistula, the presence of pseudoaneurysm, the presence of varicose veins, the form of draining veins including the presence of cortical venous drainage, the condition of collateral blood supply arteries, and the presence of combined entrapment aneurysms. A comprehensive cerebral angiogram should include a bilateral common carotid artery angiogram, selective angiograms of the affected internal and external carotid arteries, compression of the affected common carotid artery to perform a healthy internal carotid artery angiogram, and compression of the affected vertebral artery angiogram. The common carotid artery on the affected side is used to rule out the coexistence of a coexisting entrapment aneurysm, atherosclerotic stenosis, myofibrillar dysplasia, or other arterial vascular disease. Selective angiography of the affected internal carotid artery can show fistulae and draining veins, while selective angiography of the affected external carotid artery can show whether the external carotid system is also involved in the blood supply. A selective angiogram of the affected external carotid artery will show whether the external carotid system is also involved in the blood supply. Compression of the affected common carotid artery was performed by compression of the healthy internal carotid artery or vertebral artery angiography to observe the collateral blood supply of the two arterial systems through the Willis ring. In the presence of a direct carotid cavernous sinus fistula, the angiographic pattern of the cavernous sinus varies widely. The cavernous sinus may appear as a distinctly dilated sinus or as a tube directly connected to the venous sinus of the dura mater and the ophthalmic vein. In some cases, it appears as a pseudoaneurysm that fills the entire cavernous sinus space. Direct carotid cavernous sinus fistulas have higher flow and velocity, and the cavernous sinus is often rapidly visualized on cerebral angiography making determination of the location of the fistula difficult. The following measures can help to show and determine the location of the fistula: (1) Insert a common contrast tube into the internal carotid artery on the affected side, compress the common carotid artery on the proximal side of the catheter tip, and then inject the contrast agent at a rate of 1 ml/s to slowly visualize the internal carotid artery and fistula distal to the tip of the tube, so that the exact location of the fistula can be observed more easily. (2) Selective insertion of a double-lumen catheter with a balloon into the internal carotid artery, filling the balloon and then injecting the contrast agent at the aforementioned rate, can also clearly show the location of the fistula. (3) Huber method: compression of the common carotid artery on the affected side and vertebral artery angiography with contrast retrograde through the posterior communicating artery to show the location of the fistula. Combining foreign data, fistulae are found in the posterior ascending segment (segment 5) in about 40% of cases, while the anterior curvature and anterior ascending segment (segments 2 and 1) in only 6% of cases. Therefore, Parkinson’s statement that fistulas are mostly anterior to the internal carotid artery in the cavernous sinus segment is not very accurate. The size and location of the fistula is important when developing a treatment plan. Most direct carotid cavernous fistulas can be successfully occluded with a balloon. If the balloon cannot enter the fistula, a guided microcatheter can be used to enter the cavernous sinus through the fistula and place a microspring coil to fill the cavernous sinus. Some small, slow-flowing carotid cavernous sinus fistulas can be cured by compression of the common carotid artery alone. Large fistulas or dissection of the internal carotid artery require occlusion of the internal carotid artery. Pseudoaneurysms or abnormal dilatation of the cavernous sinus can lead to fatal rhinorrhea and intracranial hemorrhage and should be treated aggressively. The presence of an entrapped aneurysm often influences the treatment options for carotid cavernous sinus fistula. If the contralateral side is combined with a coarctation aneurysm, the affected internal carotid artery cannot be occluded in the treatment. If the internal carotid artery cavernous sinus segment is involved near the fistula, the fistula should be occluded along with the internal carotid artery. It is important to fully understand the establishment of collateral circulation when occluding the internal carotid artery. The form of venous drainage is closely related to clinical symptoms. A carotid cavernous sinus fistula with supraocular venous drainage usually has typical ocular signs and symptoms. Those with superior and inferior rocky sinus drainage are prone to cerebral nerve palsy symptoms. In contrast, those with cortical venous drainage are prone to intracranial hemorrhage, intracranial hypertension and neurological dysfunction. 2.CT and MRI examination On enhanced CT or MRI, you can see obviously dilated ophthalmic veins, protruding eyeballs, congested and thickened extraocular muscles, swollen eyelids, bulbar conjunctival edema, significantly increased density or signal of paracentral structures, thickened cortical drainage veins and accompanying cerebral edema, as well as traumatic changes of the skull and skull base fractures, brain injury and intracranial hematoma. Transcranial Doppler ultrasound provides a noninvasive, real-time view of the hemodynamic parameters of carotid cavernous sinus fistulas: (1) Measurement of the flow velocity of the affected internal carotid artery, including systolic flow velocity Va, diastolic flow velocity Vd, and pulsatility index PI. The beat-to-beat index was reduced to below 0.5. Indirect fistulas may have normal or insignificant changes in flow velocities and resistance indices. (2) Transorbital measurement of the abnormal spectrum of the periorbital veins can assist in the diagnosis of carotid cavernous sinus fistula. The ophthalmic and periorbital veins are the most common draining veins in carotid cavernous sinus fistulas. Arterialized flow signs of high flow velocity and low resistance in the superior ophthalmic vein can be found, with flow velocity almost one times higher than the normal side and a pulsatility index that is reduced by about half and returns to normal when treatment is effective. (3) Detection of intracranial blood flow through the temporal window provides insight into blood theft and reveals increased mean blood flow velocity in the middle cerebral artery, anterior cerebral artery and contralateral anterior cerebral artery, reversal of blood flow direction in the ipsilateral anterior cerebral artery, and opening of anterior and posterior communicating arteries. (4) Indicate the direction of blood flow, TCD can not only detect blood flow velocity, but also indicate the change of blood flow direction, thus it can be used to determine the situation of collateral circulation and the direction of blood flow in the draining vein. tcd test is helpful for early diagnosis of carotid cavernous sinus fistula, selection of treatment plan and evaluation of efficacy. Single photon emission computed tomography (SPECT) is a non-invasive method for the examination of cerebral perfusion and cerebral metabolism. It uses radionuclides such as 99mTcHMPAO to detect cerebral perfusion before and after endovascular treatment of carotid cavernous sinus fistula and to evaluate the efficacy. The Matas test is used to reflect the status of collateral circulation. If the reduction of radionuclides in the anterior cerebral artery and middle cerebral artery supply area is less than 15%, occlusion of the carotid artery does not produce symptoms of neurological deficit. Therefore, SPECT is a useful guide for the diagnosis and treatment of carotid cavernous sinus fistula.