Arteriovenous malformations (AVMs)
An arteriovenous malformation (AVM) is an abnormal tangle of blood vessels connecting arteries and veins. This tangle can disrupt normal blood flow and oxygen circulation, that can lead to health problems.
What are arteriovenous malformations?
An arteriovenous malformation (AVM) is an abnormal tangle of blood vessels at the junction where arteries and veins meet.
Because an AVM disrupts the normal flow of blood and circulation of oxygen around the body, problems can occur.
Surrounding tissues may not get enough oxygen, and the tangled blood vessels that form the AVM may weaken and burst.
This rupture can cause serious health problems, especially if the AVM is in the brain.
If an AVM in the brain ruptures, it can cause bleeding in the brain (haemorrhage), stroke or brain damage.
What causes arteriovenous malformations?
The exact cause of an AVM is not completely understood yet. But most AVMs are thought to develop before or shortly after birth. An AVM is not a condition that develops later in life.
Some AVMs are detected by accident during an investigation for an unrelated illness.
How common are arteriovenous malformations?
Arteriovenous malformations are quite rare. They occur in about 18 out of 100,000 people, and only two of these people will show any symptoms.
In comparison, stroke affects 2,500 out of 100,000 people, showing just how rare it is to become ill because of an AVM.
What are the symptoms of arteriovenous malformations?
Symptoms of an arteriovenous malformation depend on where it’s located in the body. But often the first signs and symptoms appear after blood vessels rupture and bleeding occurs.
If you have a brain AVM, symptoms may be more noticeable. These include:
- Epileptic seizures – these can occur because tiny bleeds from a small AVM disrupts the way the brain works
- A headache that’s quite like a migraine – this also tends to occur when the AVM is small
- Back pain – that has no other explanation
- Tinnitus – ringing or buzzing in your ears
- Unexplained symptoms linked to the nervous system – feeling weak, losing your balance, dizziness, poor memory, experiencing numbness or tingling
If you do experience symptoms and a brain AVM is diagnosed, your consultant may recommend your symptoms are managed rather than treated with brain surgery.
Different medication your consultant may prescribe to help you with your symptoms include:
- Painkillers for back pain and headaches
- Anti-nausea medication for nausea or vomiting that comes with headaches
- Anticonvulsants for seizures
None of the treatments to manage symptoms will affect the size or severity of an AVM itself.
If an AVM in the brain is in danger of causing a large bleed, various surgical treatments are likely to be offered.
How are arteriovenous malformations diagnosed?
Currently, many arteriovenous malformations are found by chance, often after a CT or MRI scan is carried out for reasons not directly related to the AVM.
We also know that around 70% of people with an AVM have their condition diagnosed after they have a stroke.
If you experience symptoms linked to a brain AVM, your doctor will review your symptoms and conduct a physical examination.
If a brain AVM is suspected, you may undergo a series of imaging tests, such as a cerebral arteriography, CT scan and MRI scan.
If an AVM is diagnosed but it’s not bleeding, it may need to be monitored very closely to follow its progress.
If you have an AVM that’s in danger of bleeding a lot, you may need treatment to try to remove it.
How are arteriovenous malformations treated?
Only around 12% of people who have an AVM will have symptoms that are so serious that the AVM needs to be treated.
Treatment options for a brain AVM include:
- Surgery Brain surgery involves opening a hole in the skull to gain access to the brain.
- Your neurosurgeon then operates on the AVM using a microscope and microsurgical techniques. The goal is usually to completely remove the AVM.
Surgery is followed by a brain test (cerebral angiogram) to check the blood flow through the brain is stable and the AVM is gone.
At The London Clinic, we can carry out incredibly precise stereotactic radiosurgery with a machine called CyberKnife.
CyberKnife is very useful for treating small AVMs, making major brain surgery unnecessary.
This is where highly focused beams of radiation are used to destroy blood vessels to stop the blood supply to the AVM.
Endovascular embolisation is used for large AVMs that are difficult to treat with surgery.
A thin tube (catheter) is placed into an artery in the groin area and passed to the AVM in the brain. A special substance is then injected through the tube to block off the artery that leads to the AVM. This may shrink the AVM, to reduce the risk of a major bleed in the brain.
As the AVM gets smaller, symptoms usually improve and the AVM may eventually become suitable for surgery which will aim to remove it completely.