What is an arteriovenous malformation (AVM)?
An arteriovenous malformation, or AVM, is an abnormal tangle of vessels in the brain or spinal cord in which one or more arteries are directly connected to one or more veins. Arteries carry blood from the heart to the tissues and veins take blood back from the tissues to the heart. In an AVM, the direct connection between one or more arteries and veins gives rise to many problems. The most serious problem is that veins are typically thin-walled vessels that cannot accept high-pressure blood flow for extended periods. The result is that AVMs can rupture and bleed into the brain.
Diagnosis of an arteriovenous malformation (AVM)
Johns Hopkins estimates that less than one percent of people are born with a brain or spinal cord AVM. Although AVMs are congenital (which means that patients are born with it), they are not hereditary (which means that they are not passed from parents to children). Most AVMs declare themselves by bleeding in adults younger than 40 years old. Some AVMs declare themselves by causing seizures or headaches. We attempt whenever possible to identify and eliminate AVMs before they bleed. We typically find the AVM in a computed tomography (CT) scan or, more commonly, in a magnetic resonance imaging (MRI) scan. If we find an AVM by CT or MRI, we then obtain an angiogram. An angiogram (also called arteriogram) is a special test in which a neuroradiologist injects dye into the blood vessels in the brain and obtains images of the blood vessels. At this point, the angiogram is the test that most accurately shows the AVM and its relationship to the surrounding arteries and veins.
Treatment for arteriovenous malformation (AVM)
At Johns Hopkins, we treat AVMs using a combination of three methods, depending on the type of AVM:
- Microsurgical resection — the most established of the three techniques. During microsurgical resection, we perform a craniotomy and remove the AVM from the brain or spinal cord using a microscope.
- Stereotactic radiotherapy — a more recent technique for the treatment of AVMs. It is also known as "stereotactic radiosurgery." During this treatment, we deliver a concentrated dose of radiotherapy to the core of the AVM in one session. Over the course of 2 to 5 years, the vessels of the AVM clot off and the AVM shuts down.
- Endovascular embolization — also a more recent technique for the treatment of AVMs. During this treatment, we pass a catheter through the groin up into the arteries in the brain that lead to the AVM and inject a material into these arteries. This injection shuts off that artery and reduces the flow of blood through the AVM. Endovascular embolization by itself typically does not eliminate the AVM and is therefore almost always used as a preliminary step in preparation for either microsurgical resection or stereotactic radiotherapy.
The cerebrovascular team at Johns Hopkins evaluates each AVM patient to decide the best singular procedure or combination of treatments for the patient's specific AVM.