Weill Medical College of Cornell University

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Arteriovenous Malformation

Arteriovenous malformations (AVMs) are abnormal collections or tangles of blood vessels in which blood does not follow its normal path, but instead flows directly from arteries into veins, without passing through interconnecting capillaries. AVMs are uncommon; approximately 2500 new cases of symptomatic AVMs are identified each year in the United States. It is not known how many people may have AVMs who have not yet experienced symptoms.

When an AVM occurs in the thick, leathery covering that surrounds the brain, called the dura matter, they are known as dural AVMs. Unlike most cerebral AVMs, these are not thought to be genetic in origin. Rather, they appear to be acquired as a result of trauma, infection, or surgery. They often occur when a portion of the circulatory system in the brain becomes obstructed with a blood clot and the body grows new blood vessels to bypass the area. This process, known as revascularization, can lead to the development of AVMs. AVMs that are located in the spinal cord will cause neurological symptoms, such as back pain, sensory loss, and weakness in the lower extremities that worsen over months and years. A percentage of these AVMs (10 to 20 percent) will cause a sudden onset of symptoms rather than a slow progression. In these cases, a vessel may have burst, causing bleeding (a hemorrhage) and resulting in weakness, numbness, and other neurological defects.

Diagnosis

Angiography, which provides an image of blood flow in the brain, is the most important diagnostic tool for AVMs; it provides important information about both the location and structure of the malformation. Specialized forms of angiography may be used to provide greater detail. Neurologists also use magnetic resonance imaging (MRI) or computed tomography (CT) to identify the malformation. Taking the patient's clinical history, symptoms, physical examination, and diagnostic studies under careful consideration,a treatment plan is formed.

Symptoms

Symptoms usually appear in mid-life and slightly more often in men than in women. When AVMs do become symptomatic, however, they often present serious problems. The most frequent presenting symptoms of an AVM are those related to an intracranial hemorrhage, or bleeding in the brain, which is a serious neurological emergency. Between 50 and 75 percent of patients with an AVM will have the malformation identified after a hemorrhage. Another common presenting symptom is seizure, especially in patients with large AVMs. Headache is also commonly associated with AVMs.

Treatment

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. Our team is an authority in the management of this problem and provides internationally recognized care. We will help guide your treatment by recommending the most effective therapies. There are a number of surgical techniques, which may be used in combination, for the treatment of AVMs. Some AVMs will require just one of these therapies and others will require a combination of therapies. Treatments include:

Stereotactic Radiosurgery

Without entering the skull, neurological surgeons can use stereotactic radiosurgery (highly targeted radiation therapy). This technique, appropriate for a smaller AVM, is effective in up to 80 percent of patients treated. It can result in the AVM's complete obliteration over a period of 1-2 years after treatment, and given the proper dosage, side effects are usually moderate and limited. This is a rapidly developing technique, requiring the most highly trained surgeons utilizing the most sophisticated equipment – such as a gamma knife, proton beams and linear accelerators – and is usually only available in major medical centers.

Embolization

Another approach, endovascular embolization, involves the insertion of a catheter, or tube, through an artery in the groin. The tube is guided up the circulatory system to the site of the AVM, where it delivers a kind of "glue" that embolizes, or blocks blood flow to the malformed vessel, thus restoring normal circulation. Embolization often is used before surgery. Sometimes, embolization may reduce the size of a large AVM sufficiently to make radiosurgery a viable option, thus avoiding surgical resection.

Microsurgical Resection

Microsurgical resection of the AVM, in which surgeons enter the skull to remove the abnormal vessels, may be safer and more effective after embolization. Following this procedure, close monitoring and strict control of blood pressure are required, as well as a high-quality angiogram to determine that the AVM has been completely removed.

After your surgery or neuroendovascular procedure, our medical care team will monitor your progress and conduct tests to evaluate the success of your therapy. We understand that the recovery period can be a physically and emotionally challenging time. We believe that the trust and cooperation built up over the weeks leading up to the surgery is an important part of the post-treatment phase. Throughout your journey, we will make decisions together to provide you with the most advanced treatments and the best possible quality of life.