The Facts

• According to the American Heart Association, AVMs occur when the connections between arteries and veins in the brain are altered. Normally, arteries in the brain feed into small vessels called capillaries, which disperse oxygen-filled blood inside the brain and allow it to function properly. Oxygen-depleted blood is then picked up by veins within the brain and transported back toward the lungs and heart. In individuals with cerebral venous malformations, additional abnormal veins are present that are either enlarged or anchored in non-functional locations.
  
  

Detection

• To detect a cerebral venous malformation or other form of AVM, doctors may order either a computed tomography (CT) scan or a magnetic resonance imaging (MRI) scan of the brain. In addition to detecting the presence of an AVM, these tests can determine the size of a malformation and whether it has ruptured. Doctors may also choose to perform a procedure called cerebral angiogram. At the start of this test, a thin tube called a catheter is inserted through an artery in the leg and guided up the body to the blood vessels in the neck. Doctors will then use this catheter to inject a solution called a contrast material, which causes the brain's blood supply to stand out clearly on imaging tests.
  
  

Significance

• Cerebral venous malformations can occur anywhere within the brain, as well as on its exterior surface. Typically, these abnormal veins are not part of a normal artery/capillary connection. According to Harvard Medical School's Neurovascular Center, venous malformations are both common and generally harmless. If they are diagnosed, further treatment is not usually required.
  
  

Considerations

• While checking for venous malformations, doctors will also look for other forms of AVM. The most common and dangerous form of AVM is called a true arteriovenous malformation. Unlike cerebral venous malformations, true AVMs involve arteries that bypass the normal capillary connections and feed straight back into the veins. These veins are not designed to handle the pressure of this direct connection, and the resulting force can weaken them and cause them to fail. If a true AVM ruptures, it can trigger serious consequences including bleeding in the brain, seizures, stroke and death.
  
  

Prevention

• While they are not inherited between generations, cerebral venous malformations and other forms of AVM are typically present from birth. For this reason, their presence cannot be prevented. However, if a dangerous form of AVM is detected, doctors may be able to repair it before serious consequences occur.