The human brain is like a busy functioning city, and the roads are the blood vessels within the brain. The highway into the city is the main artery, while the highway out of the city is the main vein. The roads in the city are big straight main roads, and there are also small winding branch roads. The different roads intersect and interconnect with each other. The blood vessels of the brain are similar, with arteries and veins intertwined and interconnected. While there are main roads in the city that lead straight in and out, the arteriovenous connections within the brain are different. Blood generally flows in from the arteries and has to pass through capillary beds before reaching the veins and then flowing out. However, in special cases, such as congenital anomalies, arteries and veins are directly connected, forming localized abnormal vascular clusters, similar to hairy clusters, which often do not have a normal vessel wall structure, but are formed by fibrous tissue. These vessels are like “simple roads” under construction, with a poor “road base” and “simple guardrails”, and “traffic The “traffic” can only walk along the “easy road” and cannot drive out of the road through the “turnoff”. Similarly, blood flows directly out through the vascular mass, and the brain tissue where the vascular mass is located cannot get normal blood supply, resulting in dysfunction, which is called vascular malformation. What are the dangers of vascular malformations? When blood flows directly through a vascular malformation, the brain tissue in the area cannot receive normal blood supply and often has necrosis, degeneration, and local dysfunction. Secondly, when the drainage vein is not open, or when the arterial pressure is elevated, such as during agitation or excitement, the abnormal vascular malformation may rupture and bleed, forming an intracerebral hematoma, compressing the brain tissue and causing serious consequences. Similar to the “easy road” in front of a car accident or a sudden increase in traffic flow, the “easy road” vehicles may be forced to drive off the road.