Arteriovenous malformations (AVMs) are defects in your circulatory system. The circulatory system includes the arteries, veins and capillaries that carry blood to and from the heart. An AVM is a snarled tangle of arteries and veins. It interferes with the blood circulation in an organ. AVMs can happen anywhere, but the ones located in the brain or spinal cord can have effects such as seizures or headaches. However, most people with brain and spinal cord AVMs experience few, if any, significant symptoms. The cause of AVMs is unknown, though they seem to develop during pregnancy or soon after birth. The greatest danger of an AVM is hemorrhage. Prevention can include surgery or focused irradiation therapy.

INTRODUCTION

Cerebral arteriovenous malformations, also known as AVMs, are a very serious condition that can cause major strokes, and can even be fatal. Depending on the age of the patient and the size and location of the AVM, doctors may recommend surgery for brain AVMs. If your doctor recommends surgery for you, the decision whether or not to have surgery is yours. This patient education module will help you understand the benefits and risks of this surgery, as well as the different alternative treatments.

ANATOMY

The brain is the control center of the body. It is inside of and protected by the skull. The brain is fed by many blood vessels. Generally arteries coming to the brain from the heart divide into smaller arteries. These smaller arteries in turn divide into capillaries, or very small blood vessels, that allow oxygen to be delivered to the brain. The capillaries then get together to form bigger venules, which in turn get together to form veins. These veins take blood back to the heart. AVMs are abnormal tangles of blood vessels, in which the arteries may connect directly to the veins without the intervening smaller vessels. Sometimes the blood vessels balloon, producing aneurysms.

SYMPTOMS AND THEIR CAUSES

AVMs or the aneurysms associated with them may create pressure on and compress the brain, causing seizure, weakness, blindness, and other neurological symptoms. The blood flow in the AVM is very high and that may cause the blood to go to the AVM rather than the surrounding brain. This can cause stroke-like symptoms. This is known as “steal phenomenon,” because the AVM steals needed blood from the surrounding brain. An AVM or the associated aneurysm may also cause a brain bleed, or hemorrhage, around the brain or into it. A significant percentage of people who suffer from this kind of bleeding go to nursing homes for the rest of their lives because of severe neurological problems. An AVM may be discovered when a brain CAT scan or MRI is done for the above mentioned symptoms, or for other reasons. This MRI scan shows an AVM with all the tangled vessels.

ALTERNATIVE TREATMENTS

AVMs can be treated in many different ways. Surgical treatment is the only one that immediately and definitely takes care of the problem and decreases the chances of a future bleed. Small AVMs in relatively inaccessible places in the brain may respond to radiation therapy. Radiation therapy causes the blood vessels to clog and the risk of bleeding to decrease. This does not always occur, however. More importantly, it takes between one and a half years to 2 years before the blood vessels clog. During that time, the brain is not protected from the risk of bleeding. Radiation therapy also has possible risks. It could lead to strokes near the AVM. To show the anatomy of the AVM better, an angiogram is usually done. An angiogram is a test where dye is injected in the blood vessels of the brain. If an operation is contemplated, often the radiologist doing the angiogram will attempt to clog part of the blood vessels with small particles or special glue. This part of the angiogram is known as “embolization.” This helps decrease the blood flow to the AVM and usually makes the surgery to remove the AVM easier. The location of some AVMs may not allow embolization. It is also important to understand that the embolization decreases the flow for a short time and does not constitute long-term treatment for AVMs. There are risks to angiography and embolization. These include but are not limited to strokes and bleeding. Aneurysms associated with an AVM may be treated non-surgically with small coils and balloons. These small coils and balloons are used to block off the aneurysm and prevent it from rupturing. They are placed inside or near the aneurysm through special catheters threaded through the main arteries of the brain. This type of treatment is known as endovascular treatment. The endovascular procedure is not for everyone. Your doctor will consider many factors including:

The size and location of the aneurysm,

If the aneurysm has bled,

If bleeding has happened,

Where in the brain it is located,

Your age, and

Your overall medical condition.

SURGICAL TREATMENT

An operation to take out the AVM and clip the associated aneurysms, if present, decreases the risks of future bleeding. The clip on the aneurysm isolates the aneurysm from the blood stream, allowing it to deflate. This prevents further bleeds and also takes the pressure off the surrounding brain. The operation itself is not meant to reverse the effect of any bleeding that may have occurred. It is instead meant to prevent any further bleeding. The operation consists of opening up the skull and very carefully dissecting the AVM from the surrounding brain and clipping any associated aneurysms. If the AVM has already bled, the clot is removed. The hair in the proposed area of the head is usually clipped before the skin incision is made. Holes are made in the skull and a piece of bone is taken out. The brain covering is then entered, the AVM is taken out, and the associated aneurysms, if present, are clipped. At the end of the operation, the piece of skull is placed back and the skin is closed. Your doctor will tell you how long you are likely to stay in the hospital. This depends on several factors, such as your age and medical condition.

RISKS AND COMPLICATIONS

This operation is relatively safe. There are, however, several possible risks and complications. You need to know about them just in case they happen. By being informed, you may be able to help your doctor detect complications early. The risks and complications include those related to anesthesia, and those related to any type of surgery. Risks of general anesthesia include nausea, vomiting, urinary retention, cut lips, chipped teeth, sore throat, and headache. More serious risks of general anesthesia include heart attack, stroke, and pneumonia.

Your anesthesiologist will discuss these risks with you and ask you if you are allergic to certain medications. Some of the risks are seen in any type of surgery. These include:

Infection, deep in the brain or at the skin level.

Bleeding. AVM surgery could cause significant blood loss, and transfusions may be necessary.

Skin scar that may be painful or ugly.

Other risks and complications are related specifically to this surgery. These are also unlikely; however, it is important to know about them. The likelihood of these risks depends on the location and size of the AVM. The bigger the AVM and the deeper it is in the brain, the greater the risk of complications. These complications include, but are not limited to, stroke, paralysis, weakness, inability to understand or speak, blindness, personality changes, seizures, and death. Infections may also occur. They can be limited to the skin only, or can be deep, involving the bone flap and requiring its removal, and replacement with plastic material months later. The infection can also involve the brain itself, requiring long-term antibiotics and possibly another operation. Blood clots in the legs can occur due to inactivity during and after the surgery. These usually show up a few days after surgery. They cause the leg to swell and hurt. Blood clots can become dislodged from the leg and go to the lungs, where they will cause shortness of breath, chest pain, and possibly death. It is extremely important to let your doctors know if any of these symptoms occur. Sometimes the shortness of breath can happen without warning.

Getting out of bed shortly after surgery may help decrease the risk of blood clots in the legs. As stated, the operation’s aim is to prevent further bleeding. It is not intended to reverse damage already caused by bleeding.

AFTER THE SURGERY

After the surgery you will probably spend a day or two in the intensive care unit (ICU). How long you stay depends on how well you are doing. The nurses in intensive care will watch you carefully. This involves the repeated checking of your neurological status, as well as close watch over your heart and blood pressure. Later you may receive physical therapy, occupational therapy, and other therapies to aid your recovery. Whether or not you will be able to resume your usual activities depends on how well you are doing at the time of your follow-up. Your doctor will tell you how long it will take before you are healed, and when you can go back to work. This depends on your age, type of work, and medical condition, as well as other factors.

SUMMARY

Cerebral AVMs are a very serious condition that may lead to bleeding in the brain, stroke, or even death. The outcome is worse after a bleed. Therefore, it is recommended in many cases to go ahead and operate on them before a bleed. In spite of the advanced technological treatment, the outcome of AVMs that have bled remains very uncertain and potentially very bleak. However, surgery for brain AVMs can relieve a variety of serious symptoms. It can even be life saving. Brain surgery has become safer than before, thanks to advances in technology and anesthesia. However, as you have learned, complications may still happen. Knowing about them will help you detect them and treat them early if they happen.