Arteriovenous Malformations (AVMs)
An AVM is a specific type of vascular malformation that may be found in the brain. AVM stands for arteriovenous malformation or artery-vein malformation. It is a disordered tangle of arteries and veins. AVMs can occur anywhere in the brain, and no two are identical in shape, size or location.
How are AVMs formed?
AVMs are congenital, meaning that people are born with them. They appear to be related to improper development of the capillaries that connect the arteries and veins.
Are AVMs dangerous?
AVMs can potentially be very dangerous. When an AVM bleeds, the blood flows into the surrounding brain, causing a blood clot in the brain. Bleeding from an AVM can cause death or permanent disability.
How are AVMs detected?
In some cases, where an AVM is not producing symptoms, it may go undetected for much of a person's lifetime. It may be discovered only by accident on a CT or MRI scan of the brain for unrelated reasons, such as following a motor vehicle accident.
An AVM can cause severe or chronic migraine-type headaches. When the patient seeks treatment for the headache, the doctor may order a brain scan that results in the identification of the AVM.
A brain bleed is often the way AVMs come to medical attention. Bleeding from an AVM causes a blood clot in the brain, which can result in death or permanent disability. AVMs that have bled repeatedly should be treated in most cases to prevent further bleeding.
Sometimes AVMs cause symptoms by gradually producing a loss of brain function. The specific symptoms will depend on the exact location of the AVM. For example, an AVM in the area of the brain that controls vision may cause progressive loss of vision.
AVMs often result in seizures. These can range from mild episodes – a few seconds of staring off into space – to violent shaking with loss of consciousness. Sometimes seizures occur during sleep.