Brain Arteriovenous Malformation

An AVM (arteriovenous malformation) of the brain is an abnormal tangle of blood vessels in the brain connecting the arteries to the veins. The tangle of abnormal blood vessels is called a 'nidus'. If the arteries and veins are connected one-to-one without the intervening tangle of blood vessels, it is called a fistula. Because these blood vessels are abnormal, they have a tendency to rupture leading to bleeding within the brain. AVMs are not unique to the brain and can occur in other parts of the body. However, brain AVMs are unique in that they cause severe devastating effects if they rupture.

How common are brain AVMs?

Brain AVMs are rare. There are no data from India. Across the world, they occur in about 1 in 100,000 population. About 2% of all strokes are caused due to AVMs. About 2/3rds of people who develop AVMs are under 40 years of age.

Why do they occur?

We do not know why AVMs occur. It is thought that most patients are born with an AVM. But, they are not hereditary. This means people don't inherit AVMs from their parents and don't pass on to their children.

Are there any risk factors for development of AVMs?

There are no known risk factors for the development of AVMs.

What are the symptoms of a brain AVM?

Majority of the AVMs do not produce symptoms. They are discovered when a CT or MRI is done for an unrelated cause. However, in some patients, AVMs may cause the following symptoms -

• ? Seizures
• ? Muscle weakness or paralysis
• ? Loss of coordination
• ? Difficulties carrying out tasks
• ? Dizziness
• ? Headaches
• ? Visual disturbances
• ? Language problems
• ? Abnormal sensations such as numbness, tingling, or spontaneous pain
• ? Memory deficits
• ? Mental confusion
• ? Hallucinations
• ? Dementia

What is the risk of bleeding from a brain AVM?

The risk of bleeding from a brain AVM is about 1-3% every year. The risk of bleeding also depends upon the type of AVM (fistula, venous malformation, true AVM) and various other factors. Typically, there is 10%-15% risk of death and 20%-30% chance of permanent brain damage related to the bleed.

How are AVMs diagnosed?

Most AVMs are diagnosed with either a CT scan or an MRI. The definitive test to diagnose and plan the treatment of AVMs is cerebral angiography.

How are the AVMs treated?

There are different ways of treatment of AVMs

• Observation: Sometimes, not choosing any intervention and close observation may be the best treatment. AVMs are generally treated if they cause symptoms or if they have a very high risk of bleed.
• Surgery: Surgical removal of the AVM is a well established and effective treatment. A successful surgery immediately eliminates the risk of causing any symptoms in future.
• Embolization: This therapy involves filling up the abnormal arteries with a glue like material from inside during a cerebral angiogram
• Gamma knife Radiosurgery: This therapy involves focussed radiation of the AVM in one sitting. However, large AVMs cannot be treated by this modality. Also, the risk of bleeding from the AVM persists for a few months after treatment until the AVM completely closes.

Very often, a combination of the above mentioned therapies may be required to treat AVMs safely and effectively.

What doctors to consult for a brain AVM?

• Neurosurgeons specializing in vascular neurosurgery
• Interventional Neuroradiologists
• Stroke Neurologists