Arteriovenous Malformations

Just like other vascular malformations, arterio-venous malformations (AVM) are always present at birth, even if they may be asymptomatic for some time. In some rare cases, they wont manifest themselves until adulthood. The AVMs are characterized by a large number of abnormal conexions between arteries and veins. These tend to be concentrated into what is called the “nidus”. These are always very dangerous vascular anomalies. They can be very active, and they are difficult to treat and can present many possible complications, being life threatening in some cases. In general, they are classified in two groups: localised or diffused. 


What is the cause of an AVM?

The root cause or causes are still unknown. It is commonly accepted that the most likely cause is an genetic error or defect that happens early in embrionary stage. There is no link known with drugs and/or food consumed during pregnancy, or with any specific activity during this period.


When does an AVM first appear?

In general, the AVM present a harmless aspect at birth, sometimes as a lightly colored birthmark. Often times, they begin to grow during infancy and more so during puberty. Intracranial AVM (commonly referred to as brain angioma or sometimes confused with aneurysm) are most often manifested during adulthood.


What parts of the body can be affected by an AVM?

AVM are more commonly localisez as opposed to diffuse, can affect any body organe and they also affect all possible skin areas. Incidence is similar across female and male.  By order of frequency, they are more often inside the head, on the arms or legs, then the main body and finally in some internal organ. When the AVM is located in the head, it commonly affects the face and/or the neck. On the other hand, most diffuse AVMs are seen on the chest, abdomen or one of the extremities. Those affecting an internal organ, such as the brain, lungs, liver or intestines may be localised or diffused. The spinal cord can also be affected by AVMs.


How do you recognise an AVM?

In early childhood, the AVM is often in a dormant state, it ressembles and may be confused with an hemangiome. This may lead to an incorrect treatment. On a second phase, the AVM will grow and extend, their aspect becomes redish or may or take a purplish tinge. The AVM will become warm and pulsating. A thrill can be felt when the area is palpated as well as when auscultating. Often times, there’s an over growing on the area, which is hot when touching it, and veintes can appear on the surface as well. 


When should I check with an AVM specialist?

If there is any suspicion of an AVM a doctor should he consulted. In all cases this should be referred to an specialist on vascular anomalies. On our site we have some recommendations for certain countries on the “Find a Doctor” area.


What are the possible complications?

The intracranial AVM can cause severe headaches and other neurological symtoms, as well as brain bleeding. When AVM is in more external areas they often have complications in other body tissues (notably the skin), including necrosis, ulcerations, and hemorrhages. AVMs can also affect bones (ostéodystrophies) or muscles (amyotrophie) and may generate persistant pain in affected areas. At long term, the hypervascular and proliferative nature augments blood flowing and may affect the heart. This may lead to a cardiac arrest in certain cases. 


How are the AVM diagnosed? 

Clinical examination allows the physician to identify certain symtoms like hot skin and perceptive pulsation. However the best way to confirm the diagnostic is to use a Doppler echocardiography. An MRI is the best instrument of diagnostic then as it offers a maximum of information about the extent of the anomaly. The finer and more precise study is conducted through an angiography, a medical imaging technique by which a contrast product is injected which allows the doctors to view in detail the blood vessels with the help of a microcatheter.


What are the possible treatments? 

Treating an AVM is always complicated. It must be done only by specialists with experience on vascular anomalies. It is rarely indicated to do any treatments during early childhood.

When the nidus is localised, practical treatment includes full surgical resection of the AVM. This can be done sometimes after one or several embolizations to reduce blood flow and reduce hemorrhage risks. However, surgery is only recommended when the entire nidus can be resected. Otherwise, surgery is to be avoided, as it may in fact trigger an aggravation of the AVM.

When surgery is not an option, there’s a possibility to treat by doing one or more embolizations. This consists in blocking the shunts (direct connections between arteries and veins) by injecting “glue” on the vessels trying to fill up the nidus. This is performed by a neuroradiologist during an arteriography, via a catheter. While this isn’t considered aggressive surgery, there are associated risks to this procedure (including skin necrosis or nerf damage). For large, complex diffuse AVMs there are options with certain drugs that may help stabilise the AVM, however these are still at an early stage and often times have secondary effects.

Elastic contention may be indicated when the AVM affects the extremities in order to reduce the blood flow.  


Syndromes associated with an AVM 

The Wyburn-Mason Syndrome, also called Bonnet-Dechaume-Blanc Syndrome, is a rare vascular malformation of central nerf system. It associates a vascular anomaly of the retina with a brain AVM, some times also having an associated facial angime and/or an augmentation of the volume of one side of the body.

The Cobb Syndrome consists in an association of a capillar malformation at the skin (sometimes with a light brown birthmark) and an AVM at the spinal cord (which may also affect the bone and muscles).

The Parkes Weber Syndrome involves a diffuse AVM affecting a member of the body, with sever augmentation of its volume. The affected member will present also a capillar malformation at certain parts of the skin, and will be longer and larger. When the blood flow to feed the AVM becomes more intense, the heart must make a bigger effort which may lead to complications in the long term.