An arteriovenous malformation is a tangle of dilated blood vessels that directly connect arteries and veins, bypassing the capillaries (which normally connect arteries and veins).
Brain arteriovenous malformations (AVMs) may or may not cause bleeding in the brain.
They may cause headaches with or without bleeding in the brain.
Doctors do brain imaging to diagnose AVMs.
Treatment may involve surgery to remove the AVM, radiosurgery to destroy the AVM, placement of material to block the AVM's blood supply, or a combination of treatments, but observation is also an option.
Brain (cerebral) arteriovenous malformations (AVMs) are uncommon. AVMs may or may not cause bleeding.
Bleeding due to AVMs usually occurs in brain tissue (intracerebral hemorrhage), but it may occur in the space (subarachnoid space) between the inner and middle layers of the tissues covering the brain (subarachnoid hemorrhage) or into the fluid-filled spaces within the brain.
AVMs can cause seizures or headache, typically in young adults. AVMs may cause headaches with no bleeding.
Diagnosis of Brain AVMs
Brain imaging
Doctors use brain imaging to diagnose brain arteriovenous malformations. Many brain AVMs can be detected by the following:
Computed tomography (CT), done with or without a radiopaque contrast agent (which can be seen on x-rays) is injected into a vein to make the aneurysm visible on an x-ray
Digital subtraction angiography is done to confirm the diagnosis. For this procedure, x-ray images of blood vessels are taken before and after a radiopaque contrast agent is injected. Then a computer subtracts one image from the other. Images of structures other than arteries (such as bones) are eliminated. As a result, the arteries can be seen more clearly.
Unruptured AVMs are often detected when brain imaging is done for other reasons.
Treatment of Brain AVMs
Conservative management
Microsurgery, radiosurgery, and/or endovascular surgery
For cerebral arteriovenous malformations, the primary goal of treatment is to prevent hemorrhagic stroke. The risks of various treatments must be weighed against the risks of no treatment (which may include rupture, seizures, and, rarely disabling brain damage).
Treatment options include
Microsurgery to remove the aneurysm
Stereotactic radiosurgery
Endovascular embolization
A combination of these procedures
No procedure
Doctors may recommend that no procedure be done if the risk of bleeding seems low or the risk of adverse effects from treatment seems high. In such cases, the aneurysm is regularly monitored for changes that could make rupture more likely.
People who have had a ruptured AVM are usually treated with a procedure to eliminate the AVM.
Microsurgery involves removing a piece of the skull so doctors can see the AVM. Then, using a microscope, they locate and remove the AVM.
Radiosurgery is not really surgery because no incision is required. Radiation is focused precisely on the AVM and used to destroy it. Machines, such as a gamma knife and a linear accelerator, are used to produce the radiation. When a gamma knife is used, an imaging frame is attached to the person’s skull. The person lies on a sliding bed, and a large helmet with holes in it is placed over the frame. The head of the bed is then slid into a globe that contains radioactive cobalt. Radiation passes through the holes in the helmet and is aimed precisely at the AVM. A linear accelerator circles the head of the person, who lies on a sliding bed, and aims radiation precisely at the AVM from different angles.
For endovascular embolization, a thin, flexible tube (catheter) is guided to the AVM and a device (such as a coil) or material is used to prevent blood from flowing into the AVM. Endovascular embolization does not repair the AVM, but it reduces blood flow to the AVM and makes surgery, if needed, safer. It may be done before microsurgery or stereotactic radiosurgery.
