Arteriovenous Malformation Overview
An arteriovenous malformation (AVM) is a defect in the circulatory (blood flow) system characterized by an abnormal connection between the arteries and veins. AVMs are made of tangles of arteries and veins and typically form during fetal development or soon after birth.
Although arteriovenous malformations can develop in many different sites, those located in the brain or spinal cord (which make up the central nervous system) can have profound effects on the body. These are known as neurological AVMs and can occur anywhere within the brain or the brain coverings.
The biggest risk with an AVM is bleeding—between two and four percent of all AVMs hemorrhage. If an AVM bleeds it can affect a number of normal body functions depending on the location and extent of the brain injury.
If they are not treated AVMs can rupture, causing brain bleeding, a stroke or permanent brain damage. The effects depend on where the AVM is located.
Normally, arteries carry oxygen-containing blood from the heart to the brain and veins carry blood (with less oxygen) away from the brain and back to the heart. When an AVM occurs, the tangled blood vessels divert blood from the arteries directly to the veins. The abnormal/weak blood vessels dilate over time and eventually may burst from the high pressure of blood flow from the arteries. This causes bleeding into the brain. There are various types of brain AVM. The most common is known as a true arteriovenous malformation. It consists of a tangle of abnormal vessels connecting arteries and veins with no normal interning brain tissue.
Wellstar neurologists and neurosurgeons offer expert, experienced treatment for patients with arteriovenous malformations. They work closely with other specialists including vascular surgeons to assess and recommend a treatment program. Each patient’s condition is unique and your doctor will discuss the specific symptoms and outlook with you.
In some patients arteriovenous malformations do not cause symptoms and are only detected incidentally, for example in the course of treatment for another problem. But about 12% of people with AVMs will experience symptoms, which can vary considerably in severity.
The most common and potentially severe symptom is brain (inter-cranial) hemorrhage, which can result in a subarachnoid hemorrhage or intracerebral hemorrhage. If you believe you or someone is experiencing a brain hemorrhage seek immediate medical attention.
Other symptoms include:
- Muscle weakness or paralysis
- Coordination and balance problems (ataxia)
- Difficulties performing organizational tasks
- Pain or unusual sensations (tingling or numbness) throughout the body
- Vision problems
There are two primary known risk factors for arteriovenous malformation
- Congenital (from birth) genetic defects that can be passed on in families
- A history of unexplained, recurrent bleeding
Arteriovenous Malformation Prevention
There are no known ways to prevent AVMs from forming. Wellstar neurosurgeons/neurologists agree with specialists who recommend not smoking, maintaining a healthy diet and getting regular exercise in order to avoid high blood pressure. Other recommendations include avoiding blood thinners (ask your doctor before making any change in your medication), heavy lifting, and excessive alcohol.
Arteriovenous Malformation Diagnosis
Your Wellstar neurosurgeons/neurologist will want to know about any relevant signs and symptoms, your overall medical condition, lifestyle and any family history of bleeding, other types of brain defects or AVMs.
Tools and Tests
Because many patients with arteriovenous malformations experience no symptoms, diagnostic tests, including those performed for other purposes, offer the best chance for identifying AVMs.
Most AVM lesions are detected by a brain scan using two primary noninvasive imaging technologies—computed tomography (CT) and magnetic resonance imaging (MRI). A CT scan uses X-rays and computer technology to build an image of structures within the brain, while an MRI uses magnets and computer technology to give higher detail of soft issues. Additional tests include computed tomography angiogram (CTA) which includes injected a dye in order to detect the presence of AVM.
These tests can reveal essential information about the size and location of the AVM, and whether it may have bled.
Another test known as a cerebral angiogram involves inserting a catheter (small tube) through an artery in the groin. The catheter is guided into each of the neck vessels leading to the brain. Dye is injected and images of the vessels are taken, providing the physician with detailed information about a possible AVM or other condition.
Arterovenous Malformation Treatment
The question of whether to treat an arteriovenous malformation is complex. Your doctor will consider a number of factors including whether the AVM had bled, where it is located and its size (smaller AVMs can be more successfully treated than larger ones).
If there are no or very few symptoms, or if the AVM is located in a part of the brain that cannot be easily treated, your Wellstar physician and team may recommend conservative medical (non-surgical) management and monitoring.
There are several surgical options for treating an arteriovenous malformation. In some cases your neurosurgeon may recommend a combination of these approaches to achieve the best possible outcome with the lowest possible risk.
Neurosurgeons remove a section of the skull to enter the brain and remove the central portion of the AVM, causing as little damage as possible to surrounding structures. Once the skull is opened the AVM is closed off with special clips and ultimately removed. The bone is then replaced and the incision is closed.
Surgery is often recommended when an AVM is relatively small in size and is located in a superficial (not deep) portion of the brain. Those located deep inside the brain cannot typically be accessed by conventional surgery because of the risk that functional areas of the brain will be damaged or destroyed.
This is a less invasive approach that involves aiming a beam of highly focused radiation directly on the arteriovenous malformation. The radiation damages the walls of the blood vessels that comprise the AVM. Over several months the vessels degenerate as a result of the radiation and eventually close. This method is typically limited to AVMs that are less than 3.5 centimeters (about 1.5 inches) in diameter. It can take up to two years to completely obliterate the lesion in this way.
In some cases it is possible to treat part or all of the AVM by placing a micro-catheter (small tube) inside the blood vessels that supply the AVM and blocking off the abnormal blood vessels from the inside. Blocking materials include specialized medical glue, tiny coils and particles that stop the flow of blood to the AVM. The procedure can make subsequent surgical remove of an AVM safer, or it can help reduce the size to make stereotactic Radiosurgery more successful.
As always, the decision to undergo surgery must be made in view of all benefits and possible risks. Discuss options in depth with your Wellstar physicians. They are committed to helping people with AVMs fully understand the risks and benefits of treatment and make the decision that best meets their diagnosis, health status and preferences.
Ongoing Care for Arteriovenous Malformation
Patient outcomes vary depending on the location of the AVM, the severity of bleeding and the extent of neurological symptoms. Many patients who undergo surgery make an excellent recovery following several days in the hospital. During or following surgery, your neurosurgeon will perform an angiogram (an X-ray that assesses blood flow) to ensure that the AVM has been completely removed.
When rehabilitation services are required, Wellstar physical therapists, occupational therapists and speech therapists offer compassionate, comprehensive services at convenient locations. Your physician will recommend rehab/therapy as needed.
If you have an AVM quit smoking or don’t start. Wellstar offers smoking cessation classes that focus on the best quitting program for the individual.