Cerebral arteriovenous malformation (AVM) is a malformed collection of blood vessels within the brain, characterized by tangle(s) of veins and arteries. While an arteriovenous malformation can occur elsewhere in the body, this article discusses malformations found in the brain.
Symptoms of bleeding within the brain (intracranial hemorrhage) include loss of consciousness, sudden and severe headache, nausea, vomiting, incontinence, and blurred vision, amongst others. Minor bleeding can occur with no noticeable symptoms. A stiff neck can occur as the result of increased pressure within the skull and irritation of the meninges. Impairments caused by local brain tissue damage on the bleed site are possible, including seizure, one-sided weakness (hemiparesis), a loss of touch sensation on one side of the body and deficits in language processing (aphasia). A variety of other symptoms can accompany this type of cerebrovascular accident.
Generally, intense headache, perhaps coincident with seizure or loss of bodily consciousness, is the first indication of a cerebral AVM. Estimates of the number of AVM-afflicted people in the United States range from 0.1% to 0.001% of the population.
Once an AVM bleeds, the probability of rebleeding may increase. However, as long as the AVM is unruptured, the risk of hemorrhage may be relatively low.
AVMs that do not bleed may cause symptoms such as epileptic seizures, headaches, or fluctuating neurological symptoms. Many of them may even remain asymptomatic.
In the U.S., surgical removal of the blood vessels involved (craniotomy) is the preferred curative treatment for most types of AVM. While this surgery results in an immediate, complete removal of the AVM, risks exist depending on the size and the location of the malformation.
Radiation treatment (radiosurgery) has been widely used on smaller AVMs with considerable success. The Gamma Knife, developed by Swedish physician Lars Leksell, is one apparatus used in radiosurgery to precisely apply a controlled radiation dosage to the volume of the brain occupied by the AVM. While this treatment is non-invasive, two to three years may pass before the complete effects are known. Complete occlusion of the AVM may or may not occur, and 8%-10% of patients develop long term neurological symptoms after radiation.
Embolization, that is, occlusion of blood vessels with coils or particles introduced by a radiographically guided catheter, is frequently used as an adjunct to either surgery or radiation treatment. However, embolization alone is rarely successful in completely blocking blood flow through the AVM.
The benefit of invasive treatment for unruptured AVMs has never been proven, as the risk of intervention may be as high as the spontaneous bleeding risk. An international study is currently under way to determine the best therapy for patients with unruptured AVMs (ARUBA—A Randomized Trial of Unruptured Brain AVMs [www.arubastudy.org]).