Arteriovenous malformation (cerebral)

Alternative names:

AVM

Definition:

A congenital disorder of the blood vessels in the brain where there is an abnormal connection between arteries and veins. (See also cerebral aneurysm.)

Causes, incidence, and risk factors:

Cerebral arteriovenous malformation (AVM) is a congenital disorder. The cause of abnormal blood vessel development in the brain is unknown.

Arteriovenous malformations vary greatly from person to person. The size varies, from massive lesions involving multiple vessels to lesions so small they are difficult to distinguish on testing. Large malformations may have enough blood flow through them to stress the pumping ability of the heart.

There are often no symptoms until complications occur. In many cases, symptoms are related to bleeding from the abnormal vessels, which are often fragile and lack the normal supportive structure of arteries and veins. Up to 70% of people with AVM experience bleeding from the malformation at some point. Small lesions are more likely to bleed than large lesions. If a lesion bleeds once, the risk is increased that it will bleed again in the future. Intracerebral hemorrhage and subarachnoid hemorrhage are the most common results of cerebral arteriovenous malformation.

Symptoms may also occur because of lack of blood flow to an area of the brain (ischemia), compression or distortion of brain tissue by large AVMs, or abnormal brain development in the area of the malformation. There may be a progressive loss of nerve cells in the brain caused by mechanical and ischemic factors. Hydrocephalus may develop and lead to symptoms.

Cerebral arteriovenous malformations occur in approximately 3 out of 10,000 people. Large AVMs, also called angiomas, occur in males more often than in females. Although the lesion is present at the time of birth, symptoms may occur at any time. Most often, symptoms develop before age 30.