Understanding brain arteriovenous malformation
What is a brain AVM?
Our bodies contain an enormous network of blood vessels called arteries and veins that transport blood throughout the body.
Arteries carry oxygen-rich blood from the heart to the rest of our organs, and our veins bring oxygen-depleted blood back to the heart. Essential to this circuit are smaller blood vessels called capillaries, which allow blood to pass from our arteries to our veins.
A small number of people have patches of missing capillaries, meaning some of their arteries and veins are not connected properly. This abnormal connection, which resembles a tangled ball of string, is formally known as an arteriovenous malformation (AVM).
Although AVMs can occur anywhere in your body, when they occur in the brain they are called brain AVMs (also known as cerebral AVMs).
Over time, as blood flows through the AVM, it causes pressure to build up inside the tangled arteries and veins. The continuous pressure may cause one of the blood vessels to rupture, allowing blood to leak into your brain. This is a life-threatening condition that requires immediate medical treatment.
What causes brain AVMs?
Although the medical community has made significant advancements in diagnosing and treating brain AVMs, it still hasn't discovered what causes them.
Most researchers believe AVMs occur during fetal development, meaning people who have this condition were likely born with it.
What are the symptoms of a brain AVM?
Even though brain AVMs are probably present at birth, most people who have this condition experience few, if any, symptoms — and not until later in life (often in their 20s, 30s or 40s). To that end, many people who have a brain AVM are not aware of it.
For some women, pregnancy can trigger a sudden onset or worsening of symptoms, due to normal pregnancy-related changes in blood volume and blood pressure.
If an AVM is pressing up against delicate nerves or brain tissue, it can cause gradual but worsening symptoms. These progressive symptoms vary by individual, depending on where in the brain the AVM is located. They include:
- muscle weakness in one part of the body
- loss of coordination, including problems walking
- vision changes
- memory loss
If an AVM hemorrhages (ruptures), causing blood to leak into the brain, it may cause the following sudden symptoms:
- severe headache
- difficulty speaking
- weakness in an arm or leg
- unsteadiness and difficulty walking
- partial or complete vision loss
- nausea or vomiting
An AVM hemorrhage can range in severity from a very small leak that causes limited damage, to a massive leak that can lead to stroke or death if left untreated.
Generally speaking, bleeding in the brain is a potentially life-threatening condition that requires immediate medical treatment.
How are brain AVMs diagnosed?
If your doctor suspects you have a brain AVM due to your gradual or sudden symptoms, he or she will likely order one or more of the following tests:
- computerized tomography (CT) scan captures cross-sectional, X-ray images of the head and can confirm whether a hemorrhage has occurred. Your doctor may pair this scan with a special dye injected into your blood stream, so he or she can observe how well blood is flowing in your brain. This is called CT angiography.
- magnetic resonance imaging (MRI) scan captures 3-D images of your brain, and can confirm the precise location of the AVM as well as any damage to nearby brain tissue. Your doctor may use a variation of this test, called MR angiography or MRA, which shows the arteries in your brain in greater detail.
- cerebral angiogram is a minimally invasive test that combines X-rays and a special dye to see inside the arteries in your brain. It is the most conclusive diagnostic test for AVM because it allows your doctor to evaluate blood flow through the AVM in real time. It also provides more detailed images of the abnormal veins and arteries, which is important for treatment planning.
How are brain AVMs treated?
If your doctor confirms you have a brain AVM, he or she will determine whether to treat you right away or to monitor your AVM over time. Your doctor will weigh several important factors, including the size and location of the AVM (together with its potential for hemorrhage), whether there is evidence of past or current bleeding, the severity of your symptoms and your overall health.
Should you require treatment, your neurosurgeon will decide which of the following procedures is most suitable for you:
- Conventional or "open" surgery may be used if the AVM is located in a part of the brain that is easily accessible. During the procedure, a neurosurgeon first performs a craniotomy to temporarily remove a piece of the skull and gain access to the brain, then uses surgical tools to seal off and remove the AVM.
- Endovascular embolization is a minimally invasive procedure that does not require open brain surgery. During the procedure, a neurosurgeon threads a small, flexible tube called a catheter through the arteries (often starting in the groin area) until it reaches an artery that "feeds" the AVM with blood. Once the catheter is in place, the neurosurgeon injects one of several materials called embolizing agents — these include tiny metal coils and glue-like substances — to block the artery and reduce or block blood flow into the AVM.
- Radiosurgery uses radiation beams to damage, and eventually close, the blood vessels that make up the AVM. During the procedure, a high dose of radiation is aimed at the AVM and delivered in a targeted way that minimizes damage to the surrounding healthy brain tissue. Despite what the name implies, radiosurgery is not surgery in the traditional sense because the procedure does not require cutting or an incision.
Brain AVM care at Lyerly Neurosurgery
Since Lyerly Neurosurgery was founded in 1934, our physicians have cared for thousands of people who need treatment for a brain or spine condition.
Today our practice continues to build upon a legacy that blends compassion, safety and innovation. Our neurosurgeons provide the full spectrum of evidence-based care, including the latest minimally invasive procedures that can only be offered by neurosurgeons with advanced training and experience.
If you or a loved one has been diagnosed with a brain AVM, you'll find the care and support you need at Lyerly Neurosurgery. In partnership with Baptist Medical Center Jacksonville, our team provides emergency and preventive brain AVM treatment, including endovascular embolization by specialists who are fellowship trained in endovascular neurosurgery.