Definition: Dural arteriovenous fistula is a vascular disease that occurs in the dura mater and the direct arterial and venous communication with the falx, cerebellar curtain, and venous sinuses that are connected to it; the disease is also known as dural arteriovenous malformation. Classification according to the location of the fistula (Herber): ①Dural arteriovenous fistula in the posterior cranial fossa. (2) Dural arteriovenous fistula in the middle cranial fossa. (3) Anterior cranial fossa dural arteriovenous fistula. (iv) Paracavernous dural arteriovenous fistula. According to the drainage vein (D jind jian): ①Drainage to the dural venous sinus or meningeal vein. ②Drainage to the dural venous sinus and retrograde filling of the cortical vein. The medullary veins in the deep white matter of the brain are more dilated in this type, which can cause intracranial hypertension for a long time. ③Drainage directly into the cortical veins is the main cause of subarachnoid hemorrhage. (iv) With dural or venous lakes, there is often an occupying effect. Cognard (1995) classification:Type I, drainage to the dural venous sinus, blood is downstream, no obvious symptoms. type II, drainage to the dural venous sinus, if blood is countercurrent, type II a; blood is countercurrent to the cortical vein, type IIb; both are present as type IIa+ IIb). 20% intracranial hypertension, lO% intracranial hemorrhage. Type III, with direct drainage into the cortical veins and no venous dilatation. Type IV, direct drainage to cortical veins with venous aneurysmal dilatation, 65% intracranial hemorrhage Type V, drainage into the perimedullary veins of the spinal cord. 50% spinal symptoms. Bonden (1995) classification: grade I, direct drainage into meningeal veins or venous sinuses. Grade II, workmanlike + cortical venous drainage. Grade III, cortical venous drainage only. Clinical symptoms: ①Pulsatile tinnitus and intracranial murmur ( 67% ). ②Headache (50% ) due to increased intracranial pressure; irritation of meninges by dilated dural arterioles; small amount of subdural or subarachnoid hemorrhage; cortical venous drainage. (iii) Intracranial hemorrhage (20%), which may manifest as subarachnoid hemorrhage subdural hemorrhage or intracerebral hemorrhage. Associated with cortical vein rupture. ④Increased intracranial pressure due to elevated venous sinus pressure affecting intracranial venous and cerebrospinal fluid uptake; secondary venous sinus thrombosis; a huge subdural venous lake with occupying effect; and traffic hydrocephalus. ⑤ Neurological dysfunction. (vi) Epilepsy. (vii) Spinal cord dysfunction. (viii) Drainage of DAVF from the posterior cranial fossa to the spinal cord surface. ⑧Other:such as impaired cardiac function. ⑨ Pediatric DAVF is clinically characterized by high flow (traffic hydrocephalus) and venous lake (non-traffic hydrocephalus, D jind jian type IV). Cardiac insufficiency, cortical atrophy and poor prognosis, with a mortality rate of 67%. Diagnosis: TCD: The hemodynamic changes of the intracranial venous system can be understood by measuring the diameter of dilated draining veins, the observation of blood flow velocity, blood flow direction and blood flow waveform, which indirectly suggests the possibility of DAVF. CT and/or CTA: ①Discovery of cerebral white matter edema, hydrocephalus and abnormal thickened vascular shadow. ② Suggest abnormal dilatation of venous sinuses. ③Find intracranial hemorrhage. ④ Suggest concomitant abnormalities, such as bone abnormalities. M R I and/or M RA:Shows the same as CT and/or CTA, but with higher resolution. Angiography: Comprehensive cerebral angiography (including external carotid angiography) is the confirmatory test. The examination includes: (1) the location of the fistula. (ii) the supplying artery, whether it is a combined internal and external carotid artery; whether the blood supply originates bilaterally or unilaterally. Dangerous anastomosis: a. anastomosis between the middle meningeal artery and the ophthalmic artery in the supraorbital fissure; b. anastomosis between the intracranial artery through the middle meningeal artery, the cavernous sinus branch of the collateral meningeal artery and the cavernous sinus segment of the internal carotid artery; c anastomosis between the ascending pharyngeal artery and the vertebral basilar artery; d. anastomosis between the occipital artery and vertebral artery. ③. Condition of the draining veins and venous sinuses, dilatation; dysplasia; stenosis, atresia, or thrombosis. ④The entire cerebral circulation time. ⑤ Any concomitant anomalies, such as cerebral arteriovenous malformations; maxillofacial arteriovenous malformations; intradural and extradural aneurysms; multiple arteriovenous fistulas; Rendou-Osler-Weber syndrome; cranial arteriovenous malformations, etc. Indications: The purpose of interventional therapy: 1. interventional therapy alone can cure the disease. 2. relief of symptoms. 3. embolization combined with surgery and/or stereotactic radiotherapy. The following conditions require active treatment: 1. history of cerebral hemorrhage. 2. intolerable intracranial murmur. 3. progressive neurological deficits. 4. symptoms of local compression. 5. increased intracranial pressure. 6. potential risk of intracranial hemorrhage and neurological deficits. Indications for emergency management: 1. cortical venous drainage with hemorrhage. 2. multiple venous sinus and venous thrombosis or marked dilatation. 3. cavernous sinus, middle cranial fossa, and anterior cranial fossa lesions causing deterioration of vision. 4. increased intracranial pressure or progressive neurological dysfunction. Contraindications: 1. Systemic condition cannot tolerate anesthesia. 2. Current interventional techniques cannot achieve the treatment purpose. 3. Patients and family members refuse interventional treatment. Embolization treatment methods: Embolization materials 4-8 F guide catheter, blood flow guide microcatheter, guide wire guide microcatheter (10, 14,18), microcatheter 0.18 a 0.3 mm (0.007 a 0.014 inch ); liquid embolization agent (NBCA ,IBCA ,Onyx system), contrast agent (super liquefied iodine oil, iodophenyl ester, tantalum powder); detachable balloon and delivery system ( Magic series at present); Controlled detachable spring ring and detachment system (GDC, Matrix system, EDC system, hydrolysis spring ring system, water expansion ring system, etc. at present), free spring ring, etc. Microparticles (200-700μm), filament, dry dura, etc. Embolization route: transarterial, venous, combined arteriovenous embolization. Embolization points: ①Transcatheter arterial route embolization, a. Microcatheter as close as possible to the fistula, embolize the fistula to achieve anatomical cure; palliative treatment, can occlude the blood supply artery. b. The branches of external carotid artery are easy to spasm, guide wire, catheter should be as soft as possible, the operation should be gentle. c. Pay attention to dangerous anastomosis and vascular variation. ②Venous route embolization, the target area should be densely and adequately filled to prevent residual drainage; try to keep the normal drainage veins open; if the transjugular route cannot be put in place, direct puncture techniques of incising the superior ophthalmic vein, drilling the superior sagittal sinus and transverse sinus can be used. Complications ① Ophthalmic vein thrombosis and its continuation worsen ocular symptoms, mostly seen after embolization of dural arteriovenous fistula (DAVF) in the cavernous sinus area. Hormonal and anticoagulant therapy may be given. (ii) Cerebral hemorrhage, most often seen with obstruction of normal cerebral venous return, or with residual blood flow backing up into the cortex. Drug and surgical treatment should be given as appropriate. (iii) Cerebral ischemia, most often seen when embolic material enters the normal cerebral vasculature through a dangerous anastomotic vessel. ④ Cerebral nerve palsy, mostly seen when the nutrient vessels of the cerebral nerve are embolized; when using pellets to embolize the external cervical blood supply artery, the pellet diameter must be >100 μm. vasodilator therapy should be given. ⑤ Brain swelling or venous cerebral infarction, mostly seen in normal venous embolism. If there is normal drainage of venous return the venous sinus must not be embolized. ⑥Local pain after external carotid artery embolization, symptomatic treatment may be given.