Arteriovenous Malformations

OVERVIEW OF ARTERIOVENOUS MALFORMATIONS

The cardiovascular system is made up of the heart and blood vessels. The blood vessels are of three types namely: arteries, capillaries, and veins. Arteriovenous malformations occur when there are abnormalities in the blood vessels. This malformation exists between the veins and arteries and disrupts the normal process of circulation. The condition is not acquired as it is present at birth. AVMs can occur on any part of the body, some even form in the central nervous system (brain and spinal cord), resulting in headache and seizure disorders.

Arteriovenous malformations
Photo Credit: Mayo Clinic

CAUSES OF ARTERIOVENOUS MALFORMATIONS

 The exact cause of arteriovenosus malformations remain unknown though there is this belief by doctors that it begins in the womb or even a little while after birth and fully manifests as the child grows.

Children that are born with arteriovenosus malformations are usually cyanosed and by this, they experience a bluish discoloration of their skin. This discoloration is due to the fact that the blood that is circulating round their body lacks oxygen. The skin gradually darkens and becomes deep red or purple as time goes by and as the condition gets worse.

RISK FACTORS FOR ARTERIOVENOUS MALFORMATIONS

Those who have some genetic syndrome disorders have a greater chance of having arteriovenous malformations alongside. Certain genetic disorders pose a greater risk. Osler-Weber-Rendu syndrome and hereditary hemorrhagic telangiectasia are the common genetic syndromes. There have been some rare reports of arteriovenous malformations running in families but this has not been proven to be genetic as it may well be a coincidence.  

SYMPTOMS OF ARTERIOVENOUS MALFORMATIONS

The symptoms that occur in arteriovenous malformations are dependent on the site of the AVM, size of the AVM and size of the blood vessel affected in the arteriovenous malformations. The symptoms may be non-specific if it is an AVM that occurs in the brain. Other times, brain AVMs can cause headaches and seizure disorders. Because this form of AVM remains asymptomatic, it may not be noticed and so is undiagnosed except when it presents with life-threatening symptoms.

The usual symptoms seen in brain arteriovenous malformations include:

  • Bleeding in the subarachnoid space of the brain called subarachnoid hemorrhage
  • Headaches
  • Seizures
  • Onesided focal neurologic deficits such as numbness, weakness or tingling sensation
  • Confusion

When AVMs occur in other body parts, the symptoms are more evident.

Symptoms that are seen when arteriovenous malformations occur in the spinal cord and the limbs include:

Symptoms that are seen when arteriovenous malformations occur in the chest, abdomen or in an organ include:

  • Abdominal ache
  • Back ache
  • Chest pain
  • Abnormal sounds in the blood vessel involved

Some symptoms are specific to young children less than the age of two and they include:

  • Congestive cardiac failure, where there is fluid overload because the heart is unable to pump out the blood that gets into it
  • Seizures
  • Hydrocephalus, which is a brain swelling that occurs because of fluid accumulation

DIAGNOSIS OF ARTERIOVENOUS MALFORMATIONS

To be able to make a diagnosis of AVM, the doctor will also conduct physical examination and send for tests that help confirm or rule out the possibility of an AVM. Some health conditions can mimic the symptoms of AVM so it is important to exclude that.

The imaging modalities that help in the diagnosis of AVMs include:

  • CT scan: this creates concise images of the body’s interior
  • MRI: it creates images of the brain and blood vessels ( for a brain AVM, it helps to tell the location of the AVM and the affected brain structures)
  • Angiography: this enhances visualization of the blood vessels of the head and neck when a catheter is inserted and a contrast dye passed through it. (the catheter is usually passed through a blood vessel in the groin)
  • Magnetic resonance angiogram (MRA): this produces an image of the blood vessel

TREATMENT OF ARTERIOVENOUS MALFORMATIONS

The treatment modalities to be used are dependent on the age, condition and physical health of the affected individual. The goal of treatment is to avoid internal bleeding, as this can cause stroke or death.

DRUGS

Medications alone cannot cure AVMs. They are prescribed by the doctor for pain management and seizure control.

SURGERY

Surgery is done to either repair or remove the affected blood vessel. The surgery also depends on the type of AVM you have. The three surgical modalities include:

  • Conventional surgery
  • Endovascular embolization
  • Radiosurgery

AVMs that occur deep in the spinal cord or brain tissue usually require endovascular embolization. The procedure involves the insertion and direction of a catheter to occlude the abnormal connection between the artery and vein. It does not repair the AVM but rather decreases the blood flow to the AVM thereby making surgery safer.

Radiosurgery makes use of radiation- a highly concentrated radiation beam and focuses it directly on the AVM site. This radiation causes damage to the walls of the blood vessel and leaves a scar tissue which later prevents blood flow into the AVM.

LONG TERM OUTCOME

There is no prevention modality for AVM. When it occurs, symptoms should be managed and treated effectively. Early diagnosis and treatment prevent severe complications. Be compliant with your medications prescribed for bleeding problems, pain, and other complications. High blood pressure management, avoid blood thinners and have a regular appointment with a neurologist to keep track of the condition and prevent complications.

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