Arteriovenous Malformation (AVM)

An arteriovenous malformation (AVM) is a defect in the formation of blood vessels where the blood flows directly from the arteries to the veins, skipping the division into capillaries. It is a fast-flow malformation involving abnormal, dysmorphic arterial to venous communication via a nidus lacking connecting capillary bed. It is mainly sporadic, but can be seen in genetic syndrome patients.

This lesion typically appears in the head and neck region particularly in the cheek, lips, and ears, but also in other areas such as the extremities, with the hand being a common location.

Symptoms and History

Most AVM lesions are present at birth and grow in proportion to the body. They are typically warm to touch, with a pink-red cutaneous stain and a palpable thrill or audible bruit, although some cases may be asymptomatic.   

The symptoms usually depend on the location of the AVM. For example:

• Brain AVM: headaches, seizures, developmental disabilities
• Skin AVM: non-healing wound, pain
• AVM inside the nose or mouth: bleeding from the nose or mouth
• AVM on an extremity: difficulty walking, pain, functional problems

Diagnosis

Clinical Exam. As discussed above, the patient may be asymptomatic or present with a warm, pinkish-red lesion with a palpable thrill, or audible bruit. In an advanced stage, there may be ulceration, bleeding, ischemia and necrosis (causing pain and wounds that are difficult to heal), and cardiac failure.

Imaging. 

• Ultrasound with color Doppler is the first line study demonstrating a poorly defined hypervascular lesion. 
• MRI (Magnetic Resonance Imaging) of the affected area may be performed to help delineate the extent of the lesion.
• MRA or CTA may also be helpful in determining the anatomy of the malformation and surrounding structures involved.
• Angiography is performed for malformation architecture and treatment planning/interventions.

Pathology. Usually biopsy is not needed as clinical examination and imaging studies are enough for diagnosis. Biopsy of AVMs could be very dangerous due to risk of bleeding.

Genetics. AVMs are mainly sporadic, occasionally associated with RASA1 mutation. 

Treatment

AVM treatment is indicated before the disease becomes more aggressive and more difficult to treat. As the lesions grow, they involve more adjacent normal tissue, and they become complicated with symptoms such as pain, enlargement, deformity, recurrent bleeding, functional impairment, tissue ischemia and/or venous hypertension. Treatment before they reach more advanced stages is important for disease control. AVMs can be treated with embolization (often combined with surgical resection), sclerotherapy, and laser therapy for mild cutaneous involvement. The search for reliable systemic medical treatments is underway

Related Topics

Some AVMs may be linked to a group of problems called a syndrome. Some of the syndromes linked to AVMs are:

• Hereditary hemorrhagic telangiectasia (HHT)
• Capillary malformation (port wine stain)
• PTEN Mutation Hamartoma Tumor Syndrome (Bannayan-Riley-Ruvalcaba syndrome and Cowden syndrome)
• Parkes-Weber syndrome