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Inclusion Criteria:

1. The diagnosis of AVM was confirmed with digital subtraction angiography (DSA) and/or magnetic resonance imaging(MRI). 2. Patients with complete clinical and imaging data. 3. Patient or patient's legal representative agreed to collection of information for this study and signed informed consent.

Exclusion Criteria:

1. Received other treatment (surgery, embolization or SRS)before inclusion; 2. Expected survival time is less than 6 months; 3. Spinal AVMs; 4. Patients missing critical baseline and imaging data.

This study is a multi-center, prospective registry study led by Beijing Tiantan Hospital, and a number of comprehensive hospitals in mainland China, aiming to uncover the long-term outcomes of AVM in Real-World in China and to discover a standardized diagnosis and treatment process for the comprehensive treatment of brain AVMs. This study is an observational study that will last for 20 years. All patients were enrolled prospectively, and the study will not influence the choice of treatment modalities. The study cohort of this study was AVM patients aged 1-80 years. The inclusion criteria were as follows: 1. The diagnosis of AVM was confirmed with digital subtraction angiography (DSA) and/or magnetic resonance imaging(MRI); 2.Patients with complete clinical and imaging data; 3. Patient or patient's legal representative agreed to collection of information for this study and signed informed consent. The exclusion criteria were as follows: 1. Received other treatment (surgery, embolization or SRS)before inclusion; 2. Expected survival time is less than 6 months; 3. Spinal AVMs; 4. Patients missing critical baseline and imaging data. Patients will be divided into two groups: experimental group and control group. Experimental group: Patients who had received a multidisciplinary assessment to develop a treatment plan were included in the experimental group. The details were as follows: Ruptured AVMs: 1. AVMs not involved vital eloquent areas, or more than 5 mm away from functional fiber bundles, microsurgery or hybrid surgery can be performed; 2. Targeted embolization for hemorrhagic predictors could be considered as a monotherapy; embolization can be used as an adjunctive strategy to reduce flow or volume before microsurgery or stereotactic radiosurgery (SRS); 3. SRS for patients with a volume less than 10ml and not in the acute phase(< 3months) of hemorrhage. Volume-stage or dose-stage can be used for giant AVMs involving important eloquent areas; 4.Conservation can be used for AVMs that are prone to severe disability due to intervention. Unruptured AVMs: Interventions are recommended if unruptured AVMs are assessed as being at high rupture risk, or have refractory epilepsy or acceptable postoperative neurological deficits, otherwise conservative treatment is recommended. The choice of intervention strategy was the same as for ruptured AVM. Control group: Patients who had not received a multidisciplinary assessment to develop a treatment plan were included in the control group. It should be noted that the multidisciplinary team for AVM was formed in June 2018, so the prospective AVM cohort from August 2011 to June 2018 and the AVM cohort after June 2018 without comprehensive evaluation of treatment regimens by the multidisciplinary team served as the control group. An electronic data capture system (EDC) was developed and used for data collection. All the clinical baseline data and imaging data were stored through a cloud server to facilitate the input work at different locations and at different times. Follow-up was conducted at the first 3-6 months and annually after surgery by clinical visit and telephone interview. The evaluation of mRS score was conducted by neurosurgeons who have at least 5 years' experience of clinical practice and all the images were interpreted by at least 2 radiologists independently who are with at least 5 years of clinical experience in radiology center of our institute. Researchers who performed follow-up assessments were blinded to treatment modalities. The primary outcomes were as follows: modified Rankin Scale, obliteration rate, subsequent hemorrhage, complication rate (such as morbidity rate, new-onset neurological dysfunction, and radiation-related complications) at 3 months, 12 months, and 3 years after treatment. The secondary outcomes were as follows: improvement of clinical symptoms (epilepsy, headache, neurological dysfunction) at 3 months, 12 months, and 3 years after treatment. Through the final follow-up data, we could compare the short-term outcomes and long-term outcomes between experimental and control group. In addition, intra-group comparisons can be made among subgroups of different intervention strategies to explore the best individualized treatment strategies for different AVM patients. Treatment criteria for craniotomy: 1. For patients with a history of rupture and bleeding: a. If the lesion is not located in the deep functional area, surgical treatment is recommended; b. If the lesion is multi-system blood supply or high blood flow, the volume is large, and with a deep blood supply, hybrid surgery (embolization + resection) can be performed; c. If the lesion is located in the deep functional area, craniotomy is not recommended. 2. For patients with unruptured hemorrhage: a. If the lesion is not located in the deep brain tissue, and is not located in an important functional area or the fiber bundle is more than 5mm away from the lesion, then surgery or combined surgery can be performed; b. If the lesion is located in the deep brain tissue, important functional areas or fiber bundles are less than 5mm away from the lesion, craniotomy is not recommended; c. If the lesion does not have the above characteristics, surgical resection alone can be performed. Interventional embolization treatment standards: 1. Ruptured bAVM should be actively treated. If there is no need for craniotomy to clear the hematoma in the acute phase, DSA should be performed 2-6 weeks after hemorrhage, and individualized treatment plans should be developed and actively treated. 2. Unruptured bAVM, if there are bleeding-related risk factors (aneurysm or high-flow fistula), relevant risk factors should be actively treated; When stereotactic radiation is planned, when craniotomy or SRS was planned, preoperative embolization for flow reduction or volume reduction is recommended; 3. Unruptured bAVM, without the above risk factors, conservative treatment was suggested if symptoms could be well controlled. Stereotactic radiosurgery standard treatment: 1. No history of bleeding: Patients with no indications for craniotomy and with appropriate volume for radiosurgery, and poor symptom controlled. Pre-treatment imaging assessment DSA (required) and enhanced MRI was required to clarify the structure of the malformation; 2. There is a history of bleeding: the period between bleeding time and the time of consultation is less than 3 months, it is recommended to wait head-enhanced MRI and DSA were performed after the hemorrhage was absorbed (3 months) to confirm the vascular architecture. 3.Volume-stage or dose-stage can be used for giant AVMs involving important eloquent areas. Conservation standard treatment: 1. Ruptured AVMs: Patients prone to severe disability due to intervention; 2. Unruptured AVMs: Patients were assessed as having a low rupture risk, or without refractory epilepsy or with a high risk of postoperative neurological deficits.

Arms

: experimental group

Ruptured AVMs: 1. AVMs not involved vital eloquent areas, or more than 5 mm away from functional fiber bundles, microsurgery or hybrid surgery can be performed; 2. Targeted embolization for hemorrhagic predictors could be considered as a monotherapy; embolization can be used as an adjunctive strategy to reduce flow or volume before microsurgery or stereotactic radiosurgery (SRS). 3. SRS for patients with a volume less than 10ml and not in the acute phase(< 3months) of hemorrhage. Volume-stage or dose-stage can be used for giant AVMs involving important eloquent areas. 4. Conservation can be used for AVMs that are prone to severe disability due to intervention. Unruptured AVMs: Interventions are recommended if unruptured AVMs are assessed as being at high rupture risk, or have refractory epilepsy or acceptable postoperative neurological deficits, otherwise conservative treatment is recommended. The choice of intervention strategy was the same as for ruptured AVM.

: control group

Patients who had not received a multidisciplinary assessment to develop a treatment plan were included in the control group. It should be noted that the multidisciplinary team for AVM was formed in June 2018, so the prospective AVM cohort from August 2011 to June 2018 and the AVM cohort after June 2018 without comprehensive evaluation of treatment regimens by the multidisciplinary team served as the control group.

Interventions

Other: - Multi-disciplinary assessment

1. Comprehensive evaluation by multidisciplinary experts; 2. Preoperative multi-modal imaging examination was applied to determine the angioarchitecture, functional fiber bundle, and hemodynamics.