The direct communication between the carotid artery and the cavernous sinus, known as carotid cavernous fistula (CCF), is a relatively common neuro-ophthalmic syndrome. For special anatomical reasons, the cavernous sinus area is the site of most arteriovenous fistulas in the body. 80% of patients first present to the ophthalmologist with ocular signs and symptoms, such as protruding eyes, congestion, and ocular motility disorders. Sometimes inexperience leads to misdiagnosis as inflammatory pseudotumor, thyroid-related ophthalmopathy, conjunctivitis, sclerositis, etc., which delays treatment and should be brought to the attention of ophthalmologists in particular.
Carotid cavernous sinus fistula
Direct or indirect communication with the cavernous sinus can be called carotid-cavernous sinus fistula. The classification of carotid-cavernous sinus fistulas can be done from at least 3 perspectives.
(i) By etiology, it can be divided into traumatic and spontaneous carotid-cavernous sinus fistulas mostly caused by head trauma, such as car accidents and falling blows, and this classification is often used by epidemiologists;
(ii) anatomically, internal and external carotid cavernous sinus fistulas are classified, and neurosurgeons use this classification for therapeutic reasons;
(3) Ophthalmologists are divided into high-flow carotid cavernous sinus fistula and low-flow carotid cavernous sinus fistula according to the severity of clinical symptoms; the internal carotid artery also sends out dural branches in the cavernous sinus and the signs and symptoms caused by direct and indirect traffic between these dural branches and the cavernous sinus are collectively called dural cavernous sinus fistula (DCF).
Usually, high-flow fistulas are direct traffic between the internal carotid artery trunk and the cavernous sinus caused by trauma, whereas low-flow fistulas are mostly spontaneous, direct or indirect traffic between the dural artery and the small fistulae of the cavernous sinus, but this division is not always consistent. If a spontaneous rupture of the internal carotid artery trunk causes a high-flow fistula direct communication between the meningeal artery and the cavernous sinus can also manifest as clinical signs of a high-flow fistula if the flow is high and the intravascular pressure is high but these cases are relatively rare.
Epidemiology
Carotid cavernous sinus fistula
Internal carotid cavernous sinus fistulas are most common in young men with a history of head trauma, while female patients are more common in pregnant women; dural cavernous sinus fistulas are most common in middle-aged and older women, and are more common spontaneously, except for a few bilateral carotid cavernous sinus fistulas that can present with symptoms in both eyes at the same time, but generally occur unilaterally, beginning mostly in one eye, and as the disease progresses, a few can present with symptoms in both or opposite eyes. The epidemiological data related to this disease are not available.
Etiology
Carotid cavernous sinus fistulas are classified as traumatic, spontaneous, or congenital in nature.
Trauma
Indirect trauma, such as car accidents, falls, and impacts, as well as direct trauma from shrapnel and cone shears, can cause
Carotid cavernous sinus fistula
Carotid cavernous sinus fistula. Indirect trauma causes skull base fractures, where the carotid artery is held in the cavernous sinus by the meninges and tears occur; needles and cone shears from the anterior orbital region pierce the cavernous sinus and internal carotid artery directly through the supraorbital fissure. The projectile can also penetrate into the skull to pierce the cavernous sinus The rupture of the internal carotid artery often has 3 outcomes.
(1) Arterial blood enters the cavernous sinus with direct arterial and venous traffic, and this traffic can be formed immediately after the injury. This traffic can be formed immediately after the injury, or due to indirect trauma, the inner lining of the internal carotid artery is cracked and blood is infiltrated into the wall of the canal by the crack to form an aneurysm, which eventually ruptures into a fistula. In some cases, the signs and symptoms of arteriovenous traffic may appear several months after the trauma, which may fall into this category;
(ii) The fracture of the butterfly bone and the rupture of the internal carotid artery coexist and communicate with each other, and the arterial blood drains from the sinus, causing uncontrollable bleeding and death;
(③ Trauma also tears the dura mater, and the internal carotid artery blood directly enters the subarachnoid space, which may also cause death due to high cranial pressure and brain herniation. In skull base fracture, while injuring the main trunk of the internal carotid artery, the blood flow is high, and the migration to form carotid cavernous sinus fistula is a better ending The wall of the branch of the internal carotid artery in the cavernous sinus is very thin, and a slight head shock can cause rupture of the meningeal pituitary trunk or the inferior cavernous sinus artery, forming a low-flow fistula.
Spontaneous
Sclerotic aneurysms of the internal and external carotid arteries and their branches, as well as other arterial wall lesions, spontaneously form fissures or ruptures, with blood from the trunk or branches flowing directly into the cavernous sinus.
Congenital
The presence of embryonic arterial or arteriovenous traffic malformations between the internal carotid artery and the cavernous sinus can be detected after birth Symptoms can also be found in congenital arterial wall weakness that cannot withstand high arterial pressure and spontaneously rupture. Most scholars believe that the latter is the main cause of dural cavernous sinus fistula.
Pathogenesis
Under normal conditions, the cavernous sinus receives blood flow from the supraocular and infraocular veins in the orbit and drains through the supratentorial and infratentorial sinuses. When an artery communicates with the cavernous sinus, arterial blood is perfused into the cavernous sinus along with its high pressure, and the latter, being filled with arterial blood, the supraocular and infraocular veins expand under the influence of the large amount of high pressure blood, and the blood within them is directed toward the
Carotid cavernous sinus fistula
Both the anterior reflux supraorbital and infraorbital sinuses are bounded by the meninges formed by fibrous tissue, which can resist the higher intravascular pressure, and the intraorbital veins are not easily dilated by the flabby fat body surrounding them and cannot withstand the pressure, so the arterial blood in the cavernous sinus then refluxes to the superior and inferior ophthalmic veins and drains to the facial veins through the superior ophthalmic veins. As the superior and inferior orbital veins become dilated and arterialized, the intraventricular pressure increases and the resistance to the return flow of blood in the orbital veins increases, causing dilatation of the veins at all levels and edema in the orbital tissues and a series of signs. If the arteriovenous fistula is larger, the blood in the middle cerebral artery and anterior cerebral artery and ophthalmic artery on the same side will enter the venous system through the fistula, and before the collateral circulation is fully established, it can cause the insufficiency of blood supply to the affected side of the brain due to “blood theft”; the pressure of the ophthalmic artery also decreases, the blood flow is slow, and the venous pressure increases, so the ischemia and hypoxia of the eye occurs. This causes corneal degeneration, lens clouding vitreous hemosiderosis, optic nerve atrophy and other carotid cavernous sinus fistula and ocular signs appear in the affected side in the early stage, and can also occur in the healthy side in the late stage, or first seen in the affected eye and then relieved, and then alternate to the opposite side which is related to the cavernous sinus and its associated vessels.
①If the cavernous sinus is open to the supraocular vein on the same side, ipsilateral ocular symptoms appear. After a long time, arterial blood can drain through the intercavernous sinus to the contralateral cavernous sinus, and then symptoms appear in both eyes;
②If the cavernous sinus and the ipsilateral superior ophthalmic vein are not in good communication, then the ipsilateral side may be asymptomatic, and through the intercavernous sinus, it will show the contralateral eye symptoms;
(3) If the cavernous sinus blood first drains through the ipsilateral superior ophthalmic vein, then a thrombus is formed and the ocular symptoms are relieved, and the cavernous sinus passes through the intercavernous sinus to the contralateral sinus, then the ocular symptoms of the healthy side appear. In low-flow fistulas although contralateral ocular signs may appear or alternate, they are mostly not due to interventricular connections, but to small arterial and venous traffic on both sides.
The normal internal carotid artery and the meningeal artery on both sides have many branches that anastomose with each other, and the meningeal branches of the internal carotid artery, external carotid artery and vertebral artery also communicate with each other any of the arteries that traffic with the cavernous sinus, often the internal carotid artery and external carotid artery on both sides supply blood sometimes the vertebral artery is also involved in blood supply. The cavernous sinus brings together some of the intracranial veins, and when the meningeal arteries communicate with their counterpart veins, arterial blood can drain through the veins into the cavernous sinus and cavernous sinus syndrome can occur. The vascular connection of carotid cavernous sinus fistula is very complicated, especially the dural cavernous sinus fistula in some cases involves bilateral internal carotid artery and external carotid artery and even vertebral artery before treatment, should be a comprehensive examination, respectively, both sides of the internal carotid and external carotid and vertebral artery angiography, many factors to take into account, in order to receive better treatment results.
Clinical manifestations
The primary site of carotid cavernous sinus fistula is intracranial, but due to the special relationship of the orbito-cranial vein, the symptoms and signs are almost always in the eye, and most patients are first seen in the eye. The severity of the clinical signs and symptoms of the disease depends on.
(i) the location of the fistula in the cavernous sinus;
(ii) the size of the fistula;
(iii) the degree of opening of different veins to the cavernous sinus;
④The changes during abnormal arterial and venous traffic can be clinically manifested as follows.
1, pulsatile eye protrusion: high flow fistulas have this sign both sides of the eye protrusion difference is mostly between 3 to 11 mm. The direction of protrusion is mostly axial, and the eye is slightly displaced downward when the supraocular vein is more severely dilated. The protrusion of the eyeball is caused by dilated orbital veins, orbital fat and edema of the extraocular muscles. The eyeball protrudes and pulsates in synchrony with the heartbeat, and murmurs may be heard both subjectively and objectively. Compression of the ipsilateral carotid pulsation and murmur disappears. In dural cavernous sinus fistula, the protrusion of the eyeball is relatively mild and sometimes not even present, and there is usually no pulsation.
2. Ocular surface vascular irritation and red eye: this sign is present in almost every patient and is the first sign. Conjunctival edema and venous dilatation are evident immediately after the formation of a high-flow fistula. The onset of low-flow fistulae is gradual, and it is difficult to determine the date of onset, peaking after 2 to 3 weeks. The vessels are highly tortuous and dilated, with a screwy bright red or purplish red color. This is due to the fact that the vessels are filled with arterial blood and are therefore lighter in color than the usual venous congestion. The dilated vessels are radiating from the dome to the corneal rim, centered on the cornea. After a few months or years of low-flow fistulae, the vessel diameter begins to decrease, leaving only the dilated vessels near the corneal limbus. This particular form of red eye and vascular dilatation is rare in other disorders.
3, diplopia and extraocular muscle paralysis: Most cases complain of diplopia, and extraocular muscle paralysis is often the main conflict, but this paralysis is partial. Incomplete paralysis of the spreading nerve is the most common and one of the first signs to occur. The articular nerve and the talocrural nerve pass through the lateral wall of the cavernous sinus, and paralysis of these two cerebral nerves can also occur, but it is relatively rare.
4, fundus changes: due to the supraocular venous pressure increase, retinal venous reflux obstruction can cause optic disc congestion retinal vein tortuosity and retinal hemorrhage. However, due to the influence of intraocular pressure, the dilatation of the central retinal vein is much less than that of the surface of the eye. Fundus hemorrhages are usually small and can be absorbed within a short period of time. Occasionally, optic disc edema and choroidal detachment are seen. Central retinal vein pulsation is seen with pressure on the eye.
5. Scleral venous sinus congestion and increased intraocular pressure: In normal conditions, the atrial vein flows through the anterior ciliary vein and ophthalmic vein to the cavernous sinus. If arteriovenous traffic occurs, venous blood flows backwards through the atrial vein and may flow into the scleral venous sinus. The change of atrial venous reflux, widening of the scleral venous sinus and congestion is easily observed on iridocorneal keratoscopy. The color of the blood is lighter than the surface vessels of the eye, due to the mixing of atrial fluid. The intraocular pressure is related to the scleral venous pressure and can be expressed according to Goldmann’s traditional formula: IOP = resistance to flow x resistance to atrial outflow + scleral surface venous pressure. In carotid cavernous sinus fistula, the blood in the atrial fluid vein backflow, atrial fluid outflow resistance increases, scleral venous pressure also increases at the same time IOP is inevitably elevated generally for mild or moderate high IOP.
6, vision loss: vision loss is uncommon. If there is retinal hemorrhage glaucoma or choroidal detachment exists, it can lead to vision loss. The vision loss caused by retinal hemorrhage is temporary and can still be recovered when the hemorrhage is absorbed. A prolonged period of increased intraocular pressure and optic nerve damage can lead to permanent vision loss. In high-flow fistula, the ophthalmic artery can reverse the flow, and long-term ocular ischemia and hypoxia can lead to optic nerve atrophy, cataract and corneal degeneration and loss of vision.
7. Headache: l/4 to 1/2 patients report pain. The pain site is mostly limited to the frontal and orbital areas of the affected side. This is caused by the dilatation of the cavernous sinus and intracranial blood vessels, which compress the meningeal nociceptive nerve. Migraine may also occur in patients with high intraocular pressure due to glaucoma.
Complications.
Complications such as traumatic intracranial hemorrhage and skull fracture can occur in trauma-related internal carotid-cavernous sinus fistulas.
Diagnosis.
The diagnosis can be made based on the history, clinical presentation, and imaging findings, especially DSA.
Differential diagnosis.
Clinical causes of supraocular venous dilatation include many lesions other than this disease, but with less dilatation, such as dural cavernous sinus fistula, thrombophlebitis, orbital apical tumors, thyroid-related ophthalmopathy, and inflammatory pseudotumors. With the exception of dural cavernous sinus fistula, which is less severe than this disease and has a similar presentation, all other lesions have associated ultrasound findings, such as intraorbital masses and extraocular muscle hypertrophy.
Investigation
Laboratory tests
Pathological examination: The cavernous sinus segment of the internal carotid artery often has weak wall lesions, such as atherosclerosis, aneurysm, arteritis, etc. Once the artery ruptures the sinus lumen adjacent to the fistula is highly dilated, the sinus is filled with arterial blood, and the wall fibers thicken. The ophthalmic vein is subjected to arterial blood and arterial pressure, and while the vein is dilated, the surrounding fibrous tissue is proliferated and the wall is thickened. This vascular change spreads throughout the orbit. The intraorbital arterial pressure is low while the venous pressure is high and the veins are filled with arterial and venous blood flow and are brighter in color than pure venous blood. The intraorbital muscles have poor circulation, fibrous hyperplasia, and chronic inflammatory cell infiltration thickening of the extraocular muscles. Increased atrial venous pressure ripples through the scleral venous sinus, causing dilation and a state of high venous pressure and venous stasis within the eye. Increased intraocular pressure causes damage to the retinal optic disc, which may result in pathological depression, retinal edema, and other glaucomatous changes. Venous exudate accumulates in the suprachoroidal space, causing ciliary-choroidal detachment. Carotid cavernous sinus fistula will cause peripheral arterial ischemia and peripheral venous stasis, resulting in a series of pathologic changes.
Other ancillary tests
Imaging is essential in the diagnosis of secondary CCF. Typical clinical signs combined with one or more imaging findings can often lead to a correct clinical diagnosis. inferior ophthalmic vein) with the pulse in the same cycle, which is the direct evidence of arterial blood perfusion to the vein.
1.Ultrasound examination: A ultrasound shows a typical low-reflection wave between the optic nerve and the superior rectus muscle and an obvious blood flow wave, i.e., a low-faint blood flow pulsation in the dilated supraocular vein. If the wave crest is pulsating, the image above the crest may be poorly displayed. Other manifestations such as thickening of the extraocular muscles and thickening of the optic nerve may be seen.
It is difficult to detect normal supraocular veins, which are located between the superior rectus muscle and the optic nerve and are round or tubular in shape. The dilated supraocular vein extends from the supra-nasal to the supraorbital fissure. Ultrasound findings of dilated supraocular veins are accompanied by significant pulsation of the dilated vessels with probe compression, and compression of the ipsilateral carotid artery may cause the pulsation to disappear. The blood velocity and size of the supraocular venous fistula are mildly or moderately highly dilated and in severe cases can be dilated to more than 10 mm. In some cases, the inferior ophthalmic vein may also be dilated. Other ultrasound findings include thickening of the extraocular muscles of the optic nerve and, rarely, choroidal detachment.
2, CDI: Color Doppler shows the dilated superior ophthalmic vein and the arterial spectrum showing low resistance arterialized spectrum, according to the hemodynamic measurement can identify high flow fistula and low flow fistula color Doppler ultrasound can measure the blood flow parameters in SOV, IOV, namely systolic flow rate, diastolic flow rate and resistance index, follow up the changes of these parameters is important to understand the status of blood supply and determine the prognosis, is It is irreplaceable by any other imaging examination.
CT scan: CT examination can show thickened SOV and extraocular muscles, and in a few cases, enlarged cavernous sinus with increased density and clearer after enhancement. CT can also detect concomitant skull base and orbital wall fractures, thus supporting the diagnosis of traumatic CCF. However, there are many similarities between the CT signs of CCF and painful ophthalmoplegia, and an important differentiator is the pulsation of dilated veins in the former, which cannot be shown dynamically on CT. Therefore, the combination of ultrasound and CT by an experienced physician can mostly make a correct clinical diagnosis; CT shows protrusion of the eye, hypertrophy of the extraocular muscles, and thickening of the superior ophthalmic vein, which can also show enlargement of the affected cavernous sinus after enhancement. If there is head trauma, it can show orbital fracture or skull fracture on the affected side.
4.MRI: Not only can it show the morphological changes of CCF, but also the blood flow velocity is a factor of imaging: MRI imaging has the flow-void phenomenon, and the faster the blood flow velocity, the lower the signal. Dilated SOVs are low signal on T1T2-weighted images, and those with longer disease duration, intravenous thrombosis, slowed flow velocity, and medium to low signal. MRI is an important tool for examining vascular lesions, and patients with CCF can have high signal dilated cavernous sinuses and tortuous SOVs, which can be clearly diagnosed by this test alone. MRI can show the dilated superior ophthalmic vein communicating directly with the cavernous sinus.
5.DSA: Angiography is the most reliable method to diagnose CCF, also known as the “gold standard”. Selective arteriography can show the cavernous sinus and supraocular vein in the arterial phase, determine the location and size of the fistula, and provide a basis for treatment. DSA should be performed if CCF is suspected and is financially feasible, with no obvious contraindications. In DSA of CCF, the positive finding rate is 100%. The source and size of the fistula directly determines the surgical plan and the timing of the procedure. In cases of direct internal carotid artery supply, clinical symptoms are severe, with obstruction of venous return to the eye and eventual glaucoma and loss of vision. The abnormal drainage can induce seizures and other neurological symptoms, so early treatment is necessary. The prognosis for direct internal carotid artery blood supply is better with timely interventional embolization after clear diagnosis. The clinical manifestations of dural cavernous sinus fistula are closely related to the number of blood supplying arteries and the patency of the drainage. Both the internal and external carotid arteries are involved in the supply of blood to the cavernous sinus and dura mater, therefore, DSA examination of these patients often shows multiple small arteries supplying blood, ipsilateral to the opposite side or even bilaterally. The direction of fistula blood drainage is also an important purpose of DSA examination. Usually patients have drainage of the ophthalmic veins and therefore present with ocular symptoms. The subcavernous and intercavernous sinuses are also important drainage pathways. Drainage from the cortical and deep veins, although in a minority, can easily induce neurological symptoms and should be given high priority.
It should be noted that it is quite difficult to fully understand the pathophysiological process in a few cases because of the complex composition of the blood supplying arteries, many congenital vascular variants, and long medical history. DSA examination showed that the left internal carotid artery blood was directly fistulated into the cavernous sinus through the intercavernous sinus to the right cavernous sinus and drained into the right eye vein, while the left eye vein The left eye vein was not visualized. After the thrombosis of the left eye vein, the fistula blood drained to the right side of the cavernous sinus through the intercavernous sinus after the forward resistance increased, causing the pressure in the right cavernous sinus to rise, and the fistula blood drained into the right eye vein, resulting in symptoms in the right eye.
Treatment
Dural cavernous sinus fistulas have a low flow rate and a tendency to form thrombi on their own. Repeated compression of the internal carotid artery can facilitate the healing process, so most patients can be treated with simple observation or symptomatic treatment. High-flow fistulas, especially those with arteriograms that confirm “blood theft,” can produce serious signs and symptoms and should be treated aggressively.
Vascular ligation
Simple ligation of the common carotid artery or the external carotid artery through the neck has been found to be curative in some patients. Due to the complexity of the fistula blood supply, most cases cannot be completely cured or recur after healing. A more thorough method is to isolate the cavernous sinus by first ligating the internal carotid artery in the neck then opening the skull, closing the internal carotid artery with a silver clip before dividing the posterior communicating branch, removing the posterior part of the orbital apex and the superior wall of the optic canal, and clamping the ophthalmic artery with a silver clip on the lateral side of the optic nerve. The main access to the internal carotid artery in the spongy sinus segment is occluded, and this procedure is suitable for the treatment of high-flow fistulas. These methods were the first used to treat this disease and have resulted in some patients being cured or having varying degrees of relief of symptoms and signs, but in most cases they do not heal or recur and can cause cerebral ischemia and are now rarely used.
Fistula embolization
Fistula embolization eliminates the presence of fistula and is in accordance with the physiology of blood flow. Early on, non-irritating substances such as self-muscle and absorbent gelatin sponges are injected into the internal carotid artery to bring the embolic material to the fistula site and embolize it using the superior blood flow. In recent years, the femoral artery has been cannulated to determine the location of the fistula, a detachable balloon is used to embolize the fistula, and then contrast is pushed in to determine the filling situation. This technique is less invasive and has a better chance of success. Symptoms such as protrusion of the eye, murmur, and conjunctival congestion and edema can be immediately reduced, and most patients can be completely cured, but embolization of the ophthalmic artery or other branches by the balloon can cause complications such as loss of vision or cerebral loss, and death can occur in a very small number of patients.
Retrograde fistula embolization of the superior ophthalmic vein approach
Successful embolization of the fistula using a detachable balloon via retrograde cannulation of the dilated superior ophthalmic vein into the cavernous sinus has been reported. It is effective not only for internal carotid cavernous sinus fistulas but also for patients who have failed to be treated with embolization of the fistula via the carotid approach and is particularly suitable for the treatment of patients with dural cavernous sinus fistulas. The approach is to dissect the skin 2 cm deep from the supraorbital notch and find the supraocular vein above the supraorbital notch. After separation, this vein is lifted and incised to insert a guidewire, which is delivered to the cavernous sinus under x-ray surveillance, and a catheter sheath is intervened, followed by a coaxial catheter with a detachable balloon or spring ring placed in the cavernous sinus to embolize the fistula. However, treatment with this method requires waiting for the wall of the vein to thicken to withstand the stimulation of cannulation without rupture, otherwise it will cause hemorrhage and acute orbital pressure increase, requiring pressure bandaging and then embolization through the arterial approach.
Treatment of glaucoma
The fundamental treatment is the closure of the inter-arterial fissure via fistula embolization in cases where treatment is successful, with a consequent decrease in IOP and control of glaucoma. In low-flow fistulas, the main treatment is high IOP. This type of glaucoma is mostly unresponsive to drug therapy and filtering surgery can lower the IOP.
Observation alone
The prognosis for low-flow fistulas is good, with about 1/2 of cases healing spontaneously without any treatment and the other 1/2 of patients maintaining a normal life without significant pain. Except for the loss of visual function due to glaucoma, which requires active treatment, and if not treated with retrograde embolization of the superior ophthalmic vein for ocular congestion and edema or bleeding, which can be treated medically, all other cases can be observed. It is worth mentioning that arteriography, a selective imaging, can show the location of the fistula and determine the diagnosis. In some of these patients (about 1/3), the fistula is closed shortly after the imaging, the protrusion of the eye is reduced, the tortuous dilatation of the veins on the surface of the eye is improved, and the intraocular pressure returns to normal. The mechanism of fistula closure by arteriography is unclear.
Prognosis and prevention
Prognosis.
It is highly unlikely that internal carotid cavernous sinus fistulas will heal spontaneously A few patients may have symptomatic relief with carotid compression or arteriography. Closure of the fistula after transorbital venography has also been reported in some patients with concomitant supraocular venous thrombosis and disappearance of ocular signs. In a few patients, prolonged untreated fistulas may be associated with anterior orbital arteriovenous hemangiomas. In addition to visual impairment caused by corneal exposure, ischemic syndrome, and glaucoma, individual cases may suffer sudden death due to rupture of the cavernous sinus, hemorrhage, and long-term orbital venous stasis and fat edema, which can cause fibrosis of the orbital tissues with a poor prognosis, and thus should be treated with surgery as early as possible. Some delayed optic nerve damage and early cerebral nerve palsy can still be expected to be partially recovered after surgery. The dural cavernous sinus fistula can heal spontaneously in 1/2 of the patients, and its glaucoma-induced typical visual impairment is relatively rare; most patients have a good prognosis and can be observed for follow-up.