Arteriovenous malformation (AVM) is a common congenital vascular malformation with a common intracranial hemorrhage onset, accounting for about 30-82% of cases. Patients may also present with seizures, headaches, or (and) focal neurological deficits, or it may be an incidental finding. As a benign disease with an aggressive prognosis, it is the goal of our clinicians to choose a reasonable diagnosis and treatment according to the patient’s clinical presentation and imaging data, to reduce the risk of treatment, and to reduce the patient’s disability and mortality. The current status of AVM diagnosis and treatment is briefly discussed with the literature. 1. Natural prognosis, hazards and significance of AVM 1.1 Natural prognosis of AVM Understanding the natural prognosis of cerebral AVM has important practical significance for the assessment of treatment benefits and risks in specific cases. The annual bleeding rate of cerebral AVM is 2-4%, with a 10% mortality rate and 30-50% disability rate per bleeding event [2].Brown et al.3 followed 166 unruptured AVMs for up to 8.2 years, and bleeding events occurred in 18% of cases, with a mean annual bleeding rate of 2.2%, and the annual bleeding rate increased with longer follow-up, reaching a mortality rate of 29% in the bleeding group, and This was corroborated by Mast et al [4], who followed 142 ruptured AVMs (8.2 months of follow-up) versus 139 unruptured AVMs (12 months of follow-up), with 18% of the ruptured group bleeding during the observation period and only 2% of the unruptured group bleeding, with annual bleeding rates of 17.8% and 2.2%, respectively, and a much higher probability of rebleeding in ruptured AVMs than in unruptured AVMs. The relationship between AVM volume and bleeding is unclear, Spetzler et al [5] concluded that bleeding was the first manifestation in 82% and 21% of AVMs less than 3 cm compared to 3-6 cm AVMs, respectively, and intraoperative pressure measurement of the main blood supply artery was performed in 24 patients, and the pressure in the blood supply artery of small AVMs was significantly higher than that of large AVMs. Because of the high intravascular pressure, small AVMs have a higher bleeding rate and bleed more severely compared to large AVMs, but Soderman [6] et al. concluded that the risk of bleeding in AVMs increases with lesion volume.Duong [7] analyzed bleeding susceptibility factors from AVM vascular constructs, including deep AVMs, aneurysms within the aberrant vascular mass or flow-related aneurysms, deep venous drainage, a single venous drainage, stenosis of the draining vein, or venous dilatation, with deep venous drainage and high perfusion pressure within the supplying artery or aberrant vascular mass being the most potent and independent warning factors for bleeding in AVM. 1.2 Hazardousness and prognostic assessment of AVMs The rupture of AVMs is usually considered to be less severe and less life-threatening compared with ruptured intracranial aneurysms, whereas Hillman et al8 concluded that the hazard of rupture was comparable between the two, with 56% of patients recovering from ruptured aneurysms and only 48% recovering well from AVMs.Crawford et al [9] investigated 217 conservatively treated AVM patients with a mean follow-up of 10.4 years, and survival analysis showed that after 20 years this population had a 42% risk of bleeding, 29% risk of death, 18% risk of epilepsy, and 20% risk of severe disability. Because of the high risk of bleeding in AVMs, theoretically the majority of AVMs should be intervened! The management of AVM patients must consider the patient’s treatment needs from the perspective of history and vascular architecture. The recognition of high-risk factors for bleeding in AVM vascular architecture is important for making reasonable treatment choices, and targeted interventions should be given to AVMs with high-risk factors for bleeding. As a common clinical neurosurgical disease, the pathological anatomy of cerebral AVM has the following characteristics: one or more thickened blood supply arteries, a thick and tortuous vascular mass, and one or more thick draining veins. CT and MR scans of the skull can make a preliminary diagnosis of typical AVM based on the typical imaging features of malformed blood vessels. The development of non-invasive techniques such as CTA and MRA can diagnose most of the AVMs and reflect the lesion structure from multiple angles, but only through dynamic scanning can the pathological structure of AVMs be reflected more comprehensively, and it is difficult for the above examinations to provide clinical information on the pathology of AVMs from the early appearance of abnormally thickened blood supply arteries to the late stage of venous disease, due to the limitations of scan time and image post-processing techniques. It is difficult to provide clinical information on the dynamic changes in AVM from the early appearance of abnormally thickened supply arteries to the possible presence of contrast stasis within the lesion in the late venous stage. As a means of treatment or disease assessment, the above methods cannot reflect the lesion from the perspective of hemodynamics and vascular architecture, and cannot provide detailed information to guide the grading of AVM or the selection of treatment methods, and cannot provide reasonable risk assessment for the development of treatment plans. For patients with AVM who choose radiosurgery or surgery, MRI scan is particularly important for lesion localization; for follow-up cases, MRI and MRA are of high value, and foreign scholars follow up the postoperative changes of AVM by MRI and MRA, and if MRI and MRA show that the lesion disappears, then it is confirmed by cerebral angiography.2 The diagnosis and treatment of AVM patients need to investigate the blood supplying arteries, malformed vascular masses, and the treatment method. The management of patients with AVM requires a comprehensive reflection of the arteries supplying the blood, the malformed vascular mass, the draining veins, and the possible presence of high-flow fistulas, intra-lesional aneurysms, and other risk factors for hemorrhage in order to assess the risk of treatment7 . Thus, despite advances in imaging technology, cerebral angiography remains the gold standard for AVM diagnosis! With the application of new materials and the development of interventional techniques, the efficacy of neurointerventional treatment for cerebral AVM has been improved.Frizzel et al [10] analyzed 1246 cases of AVM embolization reported in the literature, and the permanent disability rates of patients treated before 1990 and those treated after 1990 were 9% and 8%, respectively. Wikholm et al [11] analyzed 150 embolization cases, with 6.7% of patients experiencing serious complications and 1.3% dying, with an overall result equivalent to 3.2 years of natural course of disease on patient survival. In unruptured AVMs, the goal of embolization is to reduce the chance of bleeding, and thus the occurrence of perioperative bleeding is unacceptable. The cure rate of AVM with a single embolization method was mostly reported as 10% or less in the literature during the period when n-BCA was widely used, but the cure embolization and adjuvant embolization rates were significantly improved after ONYX gel was applied clinically. was 5.1% and the permanent disability rate was 3.8%, all due to post-embolization bleeding [12].Maimon et al13 applied ONYX gel and a SONIC microcatheter with a detachable cephalic end for AVM embolization and included patients with Spetzler-Martin scores 1-3 in the curative embolization group, which achieved a cure rate of 55% and another group Spetzler-Martin grade 4-5 cases selected some cases for curative embolization, the group while the overall efficiency reached 37%, this group of cases represents the results obtained from the current application of mature technology and the latest materials, but the incidence of perioperative complications in this group of cases 9.2%, the incidence of permanent disability reached 6.9%, the main complications are vascular rupture caused by the catheter, guidewire operation The above indicates that as a microinvasive treatment method, endovascular embolization can be an effective treatment for some AVMs, but the safety of treatment needs to be improved and the indications for embolization treatment need to be further standardized. 3.2 Radiation therapy for AVM X-knife and gamma knife are the more common methods of radiation therapy for cerebral AVM in clinical practice, which can achieve cure by inducing the proliferation of lesioned endothelial cells followed by gradual occlusion of blood vessels. The risk of bleeding in AVM after radiotherapy is between 1.6-9%, and this process can last up to 3 years, and patients are potentially at risk of bleeding within 3 years; it is usually believed that the risk of bleeding in AVM after radiotherapy is not significantly increased compared with that before treatment, but complete imaging cure of AVM requires long-term follow-up, and the risk of hemorrhage in the class of accumulation at 5 years after radiotherapy can be 5.0-10.2%, and AVM may still bleed even if imaging is cured.2,14 The main complications after radiosurgery for AVM include epilepsy, headache, neurological impairment and radiation brain damage, and permanent neurological deficits occur in 0.4-20.6% of patients after radiotherapy; the overall effectiveness of radiotherapy for AVM has been reported in the literature to be in the range of 54%-92%, depending on the number of follow-up visits, the timing of follow-up visits and the imaging techniques applied for follow-up [15, 16,17]. Predictors of better efficacy of radiation therapy for AVM include small AVM, single venous drainage, low SM grading, high peripheral or maximum dose, male, and hemorrhagic AVM [2]. In recent years, some progress has also been made in the treatment of large cerebral AVM using a radiation approach, and Lee et al.18 treated a group of patients with large AVM who were followed up with single or fractionated sequential radiotherapy, with an overall cure rate of 35.71%, but two patients experienced bleeding and eventually died, with a mortality rate of 8.7%. It can be seen that the cure rate of radiotherapy for large AVMs is approximately comparable to that of embolization, but the incidence of serious complications is increased. Because of the latency period of efficacy after AVM radiotherapy, the risk of rebleeding cannot be relieved in time, and the presence of radiation brain damage, the efficacy for large AVM is not satisfactory, therefore, as a non-invasive treatment option, radiotherapy for AVM is still recommended for small AVM in functional areas, and also as a treatment for residual lesions after AVM embolization sequential treatment or surgery.2,17 3.3 Surgical treatment of AVM Surgical treatment of AVM has a long history of positive results, and is respected by neurosurgeons for its rapid efficacy and high cure rate compared to radiosurgery. The most clinically used evaluation system is still the Spetzler-Martin score, and the higher the score, the greater the surgical risk, with a 92-100% good prognosis for patients with grade I, while the good prognosis for patients with grade V drops to 57.1% and the mortality rate reaches 4.8%.19 Zhao Jizong et al.20 reported 1255 patients, of whom more than 70% were resected by direct vision surgery before 1992. After 1992, with the application of microsurgical techniques, the mortality rate of grade II-IV patients was 87.9%, and the mortality rate of patients operated under direct vision in the early stage was as high as 15.5%, while the mortality rate decreased to 2.1% after the application of microsurgical techniques combined with neuronavigation and intraoperative embolization. The incidence of postoperative neurological and surgery-related complications decreased from 27.7% in the early stage to 13.8%. It is usually believed that giant AVM requires combined treatment, but with the development of surgical techniques and microsurgery, some scholars proposed the method of simple surgical resection. Huo Weikang et al.20 performed direct microsurgical resection on 93 cases of large cerebral AVM, and the rate of good GOS score reached 90.1%, and the incidence of moderate or above disability was 9.9%, and concluded that there is no risk of intraoperative perfusion pressure breakthrough in large cerebral AVM. There is no need for preoperative embolization of large cerebral AVM, and the efficacy achieved in this group of cases is significantly better than that reported in other literature. Foreign scholars have also applied functional MRI and intraoperative cortical EEG detection techniques in large unruptured AVMs and AVMs in functional areas, with satisfactory results.22,23 Andreas et al.24 adopted fractionated embolization combined with surgery to treat a total of 119 AVM cases including a group of grade I-V patients, and their overall cure rate reached 96% with no fatal cases, thus the advantages of combined treatment are still apparent. The advantages of combined treatment are still evident. Due to the complexity of the lesion and the risk of surgery, surgical treatment of AVMs, especially large AVMs, is still a challenging clinical task. AVM requires safe and reasonable treatment, and the previous treatment advocates adjuvant embolization followed by surgery or radiotherapy. Surgery, neurointerventional, and neuroradiologic surgery can all be effective in some patients, but it is unlikely that either approach alone will be effective in all cases. Beijnum et al25 analyzed the treatment patterns of AVM in four treatment centers in different regions of the same country, and the treatment patterns of patients with the same Spetzler-Martin classification varied from center to center, considering local referral patterns, treatment options, and available treatment modalities. AVM treatment is an important reference, but the choice of treatment for a specific case should still be case-specific, combining standardization and individualization. As a reference, the AHA guidelines recommend surgical resection as the first choice of treatment for grade I-II patients, but radiotherapy is recommended if the risk of surgery is increased due to the lesion site or the anatomy of the blood supply artery; for grade IV-V patients, only embolization is performed to address the risk factors for bleeding and relieve clinical symptoms unless the purpose of surgery or radiotherapy is to cure the lesion. Based on the location of the lesion, the vascular architecture of AVM, the patient’s general condition and requirements, and the technical expertise of the unit, a single treatment method of surgery, embolization, or radiosurgery should be used as much as possible, or a combination of the two methods if necessary, to reduce the operational risk and postoperative complications. For class IV-V AVMs, the aim of treatment is to reduce the risk of bleeding or to alleviate clinical symptoms with an acceptable therapeutic risk, and the curative effect of a single approach is poor; for most of these patients, endovascular intervention is only part of the inertial treatment of surgery or radiosurgery, and embolization reduces the size of the lesion to make it suitable for radiotherapy or surgery to improve the efficacy and reduce surgical complications 12, 24. Large AVMs require multidisciplinary and multi-method treatment, and most large treatment centers abroad have neurosurgeons, neurointerventionalists and neuroradiologists working together to evaluate AVMs and develop treatment plans, which is a multidisciplinary cooperation to complete the diagnosis and treatment of AVM patients, and can ensure that patients receive scientific and reasonable treatment options to the greatest extent. Due to the differences in equipment between hospitals, the expertise and treatment preferences of the doctors who see them, the patients’ own treatment choices, and the objective advantages and disadvantages of different treatment methods, we advocate multidisciplinary cooperation in AVM cases to jointly provide patients with scientific treatment choices and ensure the maximum benefit for AVM patients. We also have reasons to believe that with the improvement of endovascular interventional and radiotherapy techniques and equipment, the treatment indications of microinvasive and non-invasive treatment methods will also be further broadened on the basis of enhancing the efficacy to a satisfactory level, and the treatment of AVM patients may no longer be difficult.