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The most dangerous arteriovenous malformations occur in the cerebral area or the brain. It is an abnormal connection between the veins and arteries in the brain itself which is usually congenital. No one knows the exact cause of an arteriovenous malformation. By appearances, the AVM is a collection of arterioles attached to venules (small veins) without intervening capillaries. This can result in increased pressure in the venules so that they can burst and cause internal cerebral bleeding.

AVMs can be large or small and can occur in any part of the body. In the brain, however, a rupture of an AVM is dangerous and can lead to haemorrhagic stroke or death. When the arteriovenous malformation ruptures, blood leaks into the brain and into the nearby tissues so that blood flow to the brain is compromised.

AVMs of the brain occur in less than 1 percent of individuals. They rupture in less than that number of people. The haemorrhages tend to occur most likely in those between the ages of 15 to 20 years but can occur in those people older than that. Some people with cerebral or brain AVMs also suffer from one or more cerebral aneurysms. These aneurysms can rupture as well.

Many patients with an AVM have no symptoms at all until they sustain a rupture. About half will have symptoms before the time of rupture that include symptoms of confusion, headache (that may be localized or generalized), buzzing in the ears, difficulty walking, blurry vision or double vision, seizures, dizziness, localized muscle weakness or skin numbness.

Doctors can diagnose an arteriovenous malformation by doing a complete history and neurological physical examination. A cerebral aneurysm can be identified using a cerebral angiogram which uses dye to outline the arteries and veins of the brain. A cranial MRI or CT scan can identify bleeding areas or aneurysms, if large enough. An EEG can detect the presence of abnormal electrical activity of the brain. Sometimes a magnetic resonance angiography or MRA can be done to highlight the presence of a bleeding or non-bleeding arteriovenous malformation.

The treatment for an AVM depends on whether or not it has ruptured. If it has not ruptured, doctors need to decide what the risk is that the AVM will rupture before deciding on surgery to remove it. The long term risk of bleeding is about 2-3 percent each year so you need to put this into perspective when deciding on surgery. The features of an AVM will determine whether or not the AVM should be surgically removed. If you plan a pregnancy, you should consider having the AVM removed. Bigger AVMs are more likely to bleed and your bleeding rate may be affected by your symptoms or your age.

Treatment of a bleeding AVM is considered a medical emergency. The goal of treatment is to control bleeding, remove the AVM and limit side effects from bleeding.

There are three surgical treatments available. There is open brain surgery that involves directly visualizing the AVM and removing it through surgery. Embolization involves passing a catheter up into the AVM and a substance is introduced that clots the blood within the AVM so it can't pass through or rupture. This is a popular choice for certain kinds of AVMs. Another treatment is called a stereotactic radiosurgery procedure. This uses stereotactic methods to provide a localized radiation to the AVM. This scars and shrinks the AVM so that it cannot rupture or has a less likelihood of rupturing. It is especially used for deep AVMs that cannot easily be managed with open surgery.

Doctors also use pain medications and anticonvulsant medications to control pain and seizures, respectively.

The prognosis of arteriovenous malformations depends on whether it is treated or not. If it is not caught until it bleeds, it can be fatal in 10 percent of cases. Other people can be left with permanent neurological deficits or permanent seizure disorders. If you reach the age of 40-50 and do not have a rupture, the AVM is likely to be stable and not bleed or cause further symptoms.

Complications of an AVM in the brain include damage to the brain, language difficulty, haemorrhage within the brain, persistent headache, numbness of a body part, visual changes, seizures, hydrocephalus or body weakness in one or more parts of the body.

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The author of the substantive medical writing on this website is Dr. Christine Traxler MD whose biography can be read here