A cerebral arteriovenous malformation (AVM) is an abnormal connection between the arteries and veins in the brain. This tangle of blood vessels can restrict or alter normal blood flow. Typically, blood flows from small arteries to capillaries, then into veins of increasing size and back to the heart. In AVMs, the blood flows directly from arteries into veins without passing through capillaries. As a result, blood that is under high pressure is allowed to flow through thin walled veins, and can lead to a hemorrhage.
Most people do not experience symptoms prior to a hemorrhage. If there are any symptoms, they may include:
- Whooshing or pulsing sounds in the head
- Muscle weakness
- Memory, vision, or coordination problems
- Numbness or tingling
Causes and Risk Factors
AVMs are uncommon, with only about 2500 new cases identified each year in the United States. They occur more often in men than in women and neurological symptoms generally appear between the ages of 20 and 40. The exact cause of AVMs is unknown, but the malformation is believed to develop before birth in early development.
In many cases, an AVM is discovered because of a hemorrhage, or because a CT or MRI was ordered for another reason. The decision to treat a cerebral AVM depends on its location, the risk of future complications if it is left untreated, and the extent of neurological deficits that may be associated with its treatment. There are a number of surgical techniques, which may be used in combination for the treatment of AVMs, including stereotactic radiosurgery (highly targeted radiation therapy), endovascular embolization, and microsurgical resection of the AVM. These are complex lesions and the decision how to treat depends on the location and risk of complications.