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Arteriovenous Malformations

In the normal circulation system, blood travels from arteries into capillaries and then into veins. Some arteriovenous malformations (AVMs), commonly seen on the head and neck, can appear as light stains at birth. Other types of AVMs, commonly seen on the trunk/torso or within a limb, may not be noticed until later in childhood.

AVMs may occur in our soft tissues like skin, fat and muscles as well as in organs such as the brain, lung, liver and intestines. Lesions in the brain are the most common arteriovenous malformation. AVMs in the brain sometimes do not cause any symptoms but may cause problems as the AVM becomes larger and can be life-threatening.

It is unknown what causes AVMs. People with conditions like hereditary hemorrhagic telangiectasia (HHT) or capillary malformation-arteriovenous malformation (CM-AVM syndrome) are more likely to have AVMs. There are additional genetic abnormalities that are connected with AVMs in the brain.

What do AVMs look like?

AVMs can appear in many different ways.

Often, an AVM cannot be seen. However, when soft tissue is affected, these malformations show up as a light red-pink color in infancy and childhood. With age, the skin becomes a darker red or purple color, and a firm mass appears below the area of skin discoloration.

If you rest your hand over the lesion, you will feel more warmth (compared to nearby skin) and sometimes feel the blood pulsing.

If the AVM is in an arm or leg, it may be larger than the unaffected limb.

What are possible complications of AVMs?

Possible complications of AVMs include breakdown of overlying skin with bleeding, pain and risk of infection. Extra stress on the heart may cause heart enlargement and could lead to heart failure over time.

A few common AVM locations are:

Lungs – When AVMs are in the lungs, there is also a risk for stroke or brain abscess (infection). There is also a risk for bleeding when there is AVM involvement in the lung. The highest risk happens during pregnancy when the mother’s blood pressure and blood volume increase.

Brain – Brain AVMs can bleed, causing neurologic problems such as seizure or stroke. Signs may include dizziness, headache or visual changes. Any changes in mental status or alertness need immediate evaluation.

Liver– Most individuals with liver AVMs do not require treatment because they rarely bleed or cause any other medical problems. Later in life, liver or heart failure can occur.

How is an AVM Diagnosed?

Physical examination shows that the skin covering the lesion is warm or hot to touch. Pulsation of blood flow can be felt, and an audible noise can be heard with a stethoscope.

Figuring out the extent of the lesion and identifying the core (called a “nidus”) is done through magnetic resonance imaging (MRI), magnetic resonance angiography (MRA; a specific type of MRI that looks at the flow of blood in vessels) or traditional angiography. Tests are needed for diagnosis and treatment planning.

Conditions Involving Arteriovenous Malformations

Hereditary Hemorrhagic Telangiectasia (HHT)

A genetic disorder called hereditary hemorrhagic telangiectasia (HHT) or Osler-Weber-Rendu syndrome is characterized by multiple, small arteriovenous lesions. These lesions can happen in the skin, mucous membranes (mouth, nose and gastrointestinal tract), lungs, liver, brain and other sites. Patients usually have symptoms like telangiectasias (small dilated blood vessels) of the skin and mucous membranes, and nosebleeds. Some people may have AVMs within their internal organs. At least three genes are known to cause this condition. It is usually inherited from one parent.

Capillary Malformation-Arteriovenous Malformation (CM-AVM) syndrome

Capillary Malformation-Arteriovenous Malformation syndrome (CM-AVM) is a genetic disorder that affects the blood vessels. In CM-AVM, certain types of blood vessels (capillaries) are enlarged, with multiple capillary malformations that can be seen on the skin. There can also be abnormal connections between blood vessels, resulting in AVMs. These AVMs can be internal, in the brain and spine, or can happen in the skin, muscle or bone on the trunk/torso, or in a limb as part of Parkes Weber syndrome (see below).

Parkes Weber Syndrome

Parkes Weber syndrome involves AVMs of an extremity, most commonly the leg. These patients also may have lymphatic malformations. The affected limb usually has a capillary malformation visible on the skin and is larger than the unaffected leg. The AVM of the leg may put extra stress on the heart. If untreated, this can result in heart issues that can become very serious.

Multiple tests such as MRI and MRA, CT imaging, ultrasonography (ultrasound) and echocardiogram (ECHO) are used to evaluate and monitor these syndromes. Treatment depends on each patient but may include medications and surgical procedures.

Treatment and Management

Should my child receive treatment?

People with AVMs or suspected AVMs should visit an AVM specialist. Treatment decisions must be made on an individual basis.

How are AVMs managed?

Management of AVMs depends on individual symptoms and potential complications. Both surgical and non-surgical approaches are used. AVMs generally need evaluation and treatment by a multidisciplinary team of experts. Regular follow-up is important to monitor and manage complications.

• Observation. Small lesions without symptoms are watched over time.
• Supportive care. All patients with lung AVMs need preventative antibiotics for dental procedures (including routine cleaning). Some surgical procedures, such as scopes of the digestive and reproductive tracts, should have antibiotics as well. This involves taking a single larger dose of antibiotic by mouth one hour prior to the procedure.
• Drug therapy. Some medications that have been used include doxycycline, thalidomide and its derivatives, bevacizumab, and pazopanib. The choice of medicine may be based on the genetic cause of the AVM.
• Surgical removal. This approach may be possible with certain lesions. When combined with embolization (see below), removal offers the best chance for cure. If the core of the lesion is completely removed, the lesion may never return. If complete removal of the core is not possible, the lesion may return or cause similar or different issues.
• Embolization. Embolization is an injection of material into the center of the lesion to block the blood supply to the lesion. There are several different materials that interventional radiologists can use for embolization. This is often used when the lesions are larger, and surgery is not an option.

Are there any risks associated with treatment?

Treatment is aimed to prevent future issues and improve the functioning and emotional well-being of the person. But each treatment approach has drawbacks and limitations.

• Drug therapy. Any medication has possible side effects. Before starting any medication, your provider will review side effects.
• Surgical removal. Some scarring will happen with surgery. Some procedures may also cause damage to body parts that have or are near the malformation. Bleeding during surgery is a potential complication.
• Embolization. Most patients do not have problems or serious side effects. Bleeding or bruising can happen at the catheter site. Clotting of an artery or damage to normal tissue is also possible.