Normally blood flows from the heart through large arteries to all areas of the body. The arteries branch and get smaller until they become a capillary, which is just a single cell thick. The capillary bed is where the blood exchanges oxygen and nutrients with the body tissues and picks up waste. The blood travels from the capillary bed back to the heart through veins. In AVM, arteries connect directly to veins without a capillary bed. This creates a problem called a high-pressure shunt or fistula. Veins are not able to handle the pressure of the blood coming directly from the arteries. The veins stretch and enlarge as they try to accept the extra blood. The weakened blood vessels can rupture and bleed and are also more likely to develop aneurysms. The surrounding normal tissues may be damaged as the AVM “steals” blood from those areas.
Surgery, endovascular therapy, and radiosurgery can be used alone or in combination to treat an AVM. Endovascular embolization is often performed before surgery to reduce the AVM size and risk of operative bleeding. Radiosurgery or embolization may be used after surgery to treat any remaining portions of the AVM. Your neurosurgeon will discuss with you all the options and recommend a treatment that is best for your individual case.
Although arteriovenous malformations are thought to represent a congenital abnormality, they are thought to develop over time and are rarely found incidentally in the very young. Having said this, a third of AVMs which are diagnosed due to haemorrhage are identified before the age of 20 years of age. Overall AVMs are diagnosed at a mean age of 31 years. Overall AVMs are thought to occur in approximately 4% of the population, but become symptomatic in only 12% of affected individuals.