An arteriovenous malformation (AVM) is a collection of abnormal arteries and veins usually located within the brain. Sometimes an AVM is located in the spinal cord.

Normally, blood flows through arteries, then to tiny capillaries, then into veins and back to the heart. In AVMs, the larger arteries connect directly to the larger veins. The blood in the arteries, which is under high pressure, enters the veins, which have low pressure and thinner walls. This mismatch in the pressure can cause the AVM to grow and rupture, causing bleeding into the brain. This bleeding may result in poor blood supply to brain cells, which can cause injury to brain structures.

As an AVM becomes larger, it may cause pressure on the brain. Also, blood flows more easily into the AVM than into normal brain tissue, which can direct blood away from normal brain tissue. Either of these two problems may cause neurological symptoms.

There are several treatment options for AVM. Often treatment will be a combination of the following: 

• No treatment at present time, follow-up will be done at specific intervals. 
• Embolization is the injection of a material into the abnormal arteries to block them off, so no blood passes through them. 
• Brain surgery to remove AVM. 
• Stereotactic radiosurgery (Gamma Knife): This is a special type of radiation, which precisely targets the AVM and causes it to clot off. After the treatment, complete blockage of the AVM may take months to years.

 

Content provided by UW Medicine Neurological Surgery, Seattle, Washington

An AVM is present at birth. No one knows why one develops. It is thought that perhaps these abnormal vessels develop because a vein becomes clotted during fetal development.

There are many pieces of information that the doctors need to obtain through a variety of tests in order to make a recommendation about the best treatment for the AVM. These tests include some of the following: 

• CT scan: helps determine whether bleeding into the brain has occurred and where the AVM is located.
• MRI scan: gives a detailed evaluation of the AVM and its relation to other brain structures. It will also identify any former bleeding.
• Cerebral angiogram (arteriogram): gives more details about the AVM, including how many vessels are involved.
• Somatosensory Evoked Potentials (SSEP): electrical studies of the nerves.
• Neuro-opthalomologic evaluation: a special eye exam.

 

Recovery after treatment of AVM varies by the individual patient and the type of treatment provided. You or your loved one will be evaluated after treatment for rehabilitation needs.