Cerebral vascular malformation is also called hemangioma, angiodysplasia, cerebral arteriovenous fistula, etc. It is not a real tumor, but a congenital abnormality of cerebral blood vessel development. AVMs are mostly seen in young people, some of them are asymptomatic for a long time, and some patients have epilepsy as the first symptom. Some patients have seizures as the first symptom, and then the malformed vessels rupture and bleed, resulting in symptoms and signs, and in severe cases, bleeding leads to brain herniation, which is life-threatening. In the past, one of the treatment methods was surgical resection, and the other was endovascular intervention. The stereotactic radiosurgery treatment represented by γ-knife is a new treatment method which has been recognized as safe and effective. (1) Indications: (1) Small and medium-sized AVMs less than 4 cm in diameter, located in important functional brain areas and deep brain. (2) Residual AVMs after failed craniotomy and endovascular embolization. (3) Small and medium-sized AVMs after three months of bleeding. (4) Elderly and frail people or those who cannot tolerate general anesthesia or craniotomy due to serious diseases of other important organs. (5) Some of the AVMs that cannot be operated for various reasons above large size or AVMs that are still large in volume after repeated embolization can be considered for head gamma knife fractionation or splitting treatment. (B) treatment mechanism: head gamma knife irradiation of malformed vascular mass, through a series of biological effects of blood vessels, so that the malformed vessels gradually occlusion and achieve the purpose of treatment. The pathological changes are endothelial cell damage of the malformed vessels caused by gamma radiation, which then causes the repair thickening of the connective tissue of the vessel wall, the thickening of the vessel wall, and the gradual reduction of the vessel lumen, leading to the closure of the final malformed vessels. Schneider et al. divided the process of malformed vessel occlusion after AVM gamma knife treatment into three stages: (1) vascular endothelial or subendothelial injury: mainly manifested by the endothelial cells from the vessel wall, rupture, separation or detachment. (2) Endothelial smooth muscle cell proliferation: All or most of the smooth muscle cells in the vessel lumen proliferate, causing a centripetal or eccentric narrowing of the vessel lumen. (3) Cell degeneration and stromal increase: mainly cellular degenerative changes, malformed vessels are mostly occluded with hyaline changes. (3) Efficacy: According to foreign data, about 50-65% of AVMs are occluded in the first year after treatment, 70-85% in the second year, and >90-98% in the third year. the smaller the volume of AVMs, the higher the occlusion rate in two years. the volume is less than 40mm3, the disappearance rate is 88%, where the volume is less than 10mm3, the disappearance rate is 100%, and when the volume increases to When the volume increases to 40mm3-100mm3, the disappearance rate decreases to 58%. Overall, the rate of complete occlusion after one year of gamma knife treatment AVM is close to 50%, two years of complete occlusion rate of 80%, three years of complete occlusion rate of more than 90%, the rate of epilepsy cessation or remission reached more than 50%, the rate of headache disappearance or improvement rate of 75%, the observation period re-bleeding rate of only 3%-4%, safe and reliable. (D) Treatment reaction: 20% of AVMs have cerebral edema after γ-knife treatment, and the larger the volume, the higher the incidence. Cerebral edema does not need to be treated in mild cases, and hormones and dehydrating agents are used in severe cases. Some of the cavernous hemangioma γ-knife treatment after the cerebral edema is serious and stubborn, it is worth noting that the treatment can be divided to reduce the cerebral edema. Vascular malformation after γ-knife treatment, vascular endothelial cell proliferation, vessel wall thickening, lumen narrowing and microthrombosis, finally leading to occlusion of the vascular nest, abnormal perfusion stops and circulation returns to normal. The above process usually takes 1-3 years, and individual occlusion is still present for 3-5 years. (E) complications: a. Bleeding from malformed vessels: after gamma-knife treatment, there is still the possibility of bleeding before vascular occlusion, and its bleeding rate is 2.6%, which is similar to the natural bleeding rate of 2.2-3% without treatment, so the bleeding after gamma-knife treatment is not caused by gamma-knife treatment, from domestic and foreign reports, gamma-knife treatment The rate of bleeding that occurs is similar to the natural bleeding rate of untreated AVM, and does not increase the rate of bleeding, and some reports also suggest a reduction in the incidence of bleeding. In conclusion, after gamma knife treatment for AVM, there is still a possibility of bleeding outside of complete occlusion of the malformed vessels, and although the chance of occurrence is small, it can be fatal if it occurs, and should be given sufficient clinical attention. After gamma knife treatment must be instructed to patients and family members, so that patients maintain a stable mind and stable emotions, pay attention to rest, quit smoking and alcohol, to minimize the triggering factors of bleeding. Second, radiological complications: acute complications such as seizures, headache, nausea and vomiting occur less frequently with gamma knife treatment of AVM, and even if there are these early acute symptoms, symptomatic treatment can generally disappear quickly. The radiological complications mentioned here refer to late radiological complications. From what is reported now, the chance of late radiological complications with the head gamma knife is less than with other targeted radiosurgery devices. Yamamoto et al. reported 53 cases of AVM gamma knife treatment followed up by MRI review for up to 10 years, of which 5 cases (9.4%) had delayed neurological deficit symptoms, and 3 cases occurred after 5 years of treatment. One patient with AVM in the midbrain developed unilateral Parkinsonian-like tremor 5.5 years after treatment; in one case, a large cyst formed in the AVM located in the left parieto-occipital region, and the patient developed progressive visual field narrowing and increased intracranial pressure, requiring craniotomy. One case developed diffuse white matter necrosis and hemiparesis 7 years after treatment. Four other cases with asymptomatic imaging changes were also identified. However, the AVM volume and treatment dose were not exceptional in these patients.Kihlstrom et al. also reported 18 cases of late radiological complications with angiographically confirmed AVM occlusion at 8-23 years (mean 14 years), but cyst formation was found at the original AVM site in 5 cases (28%), but the cysts were comparable in size to the original AVM size and did not cause a dominant effect and did not require surgery; 11 cases ( 61%) were found to have abnormal hyperplasia at the original site, which showed enhancement effect on enhanced MRI; 3 cases (17%) showed MRI T2 image high signal at the original site. However, none of these 18 patients showed clinical symptoms. From the available observation data, the chance of late radiological complications of head gamma knife treatment for AVM is not significant, but this possibility exists, and it is meaningful to instruct patients to observe for a long time. As long as the treatment dose is clinically controlled it should be very safe.