Arteriovenous Malformation (AVM)
About- An arteriovenous malformation (AVM) is an abnormal connection between arteries and veins. Normally, arteries carry oxygen-rich blood from the heart to the body’s tissues through smaller blood vessels called capillaries. The blood then enters veins and returns to the heart. In an AVM, arteries connect directly to veins without the normal network of capillaries between them. This abnormal connection can allow blood to flow rapidly from the arteries into the veins. Over time, the increased pressure and altered blood flow can weaken the blood vessels and may cause bleeding, particularly when an AVM develops in the brain or spinal cord. AVMs can occur in different parts of the body, but they are particularly important when they affect the brain, spinal cord, or other areas of the nervous system. Some AVMs cause no symptoms and may be discovered incidentally during tests performed for another reason. Others can cause headaches, seizures, neurological problems, or bleeding. The severity of an AVM varies considerably from person to person and depends on its location, size, blood-flow characteristics, and whether it has caused bleeding or other complications.
AVMs can occur in several locations, including:
- Brain AVM: An abnormal connection between arteries and veins in the brain.
- Spinal AVM: An AVM involving blood vessels around or within the spinal cord.
- Peripheral AVM: An AVM affecting blood vessels in other parts of the body, such as the limbs, lungs, or organs.
Brain and spinal AVMs require particular attention because bleeding or pressure on nearby nervous tissue can result in serious complications.
Some people with an AVM have no symptoms. Symptoms may develop when the AVM causes bleeding, affects surrounding tissues, or changes normal blood flow. Possible symptoms include:
- Headaches
- Seizures
- Weakness or paralysis affecting one side or part of the body
- Numbness or tingling
- Difficulty speaking
- Difficulty understanding speech
- Vision problems or vision loss
- Confusion
- Problems with balance or coordination
- Unsteadiness while walking
- Dizziness
- Memory or concentration problems
- Nausea and vomiting, particularly when associated with bleeding in the brain
- Loss of consciousness in severe cases
Symptoms can vary depending on where the AVM is located and whether bleeding has occurred.
A brain AVM can sometimes rupture and cause bleeding in or around the brain. This is a medical emergency. Warning signs may include:
- A sudden, severe headache
- Sudden weakness or numbness
- Difficulty speaking or understanding speech
- Sudden vision problems
- Loss of balance or coordination
- Seizures
- Nausea or vomiting
- Confusion
- Loss of consciousness
A sudden, severe headache or new neurological symptoms require immediate emergency medical attention.
The exact cause of most AVMs is not known. Many AVMs are believed to develop during fetal development or early in life as blood vessels form abnormally. They are generally considered developmental abnormalities rather than conditions caused by lifestyle choices. Most AVMs are not thought to develop because of common factors such as diet, exercise, smoking, or everyday physical activity. Rare inherited conditions can increase the likelihood of developing abnormal blood vessels. However, most people with an AVM do not have an identifiable inherited cause.
Because the cause of most AVMs is unknown, specific risk factors are difficult to identify. Factors that may be relevant in some cases include:
- Developmental abnormalities of blood vessels
- Certain rare inherited vascular conditions
- A family history of specific vascular disorders
An AVM is not generally considered something that can be prevented through lifestyle changes.
An AVM can remain stable for many years, but some can cause serious complications.
One of the most serious complications of a brain AVM is intracranial haemorrhage, or bleeding inside the skull. Blood may collect within the brain or in the spaces surrounding it. Bleeding can cause permanent brain injury and may be life-threatening.
If bleeding occurs into the space between the brain and its surrounding membranes, it can result in a subarachnoid haemorrhage. This may cause a sudden and extremely severe headache, often described as a “thunderclap” headache.
An AVM can irritate or damage nearby brain tissue and may lead to seizures.
Depending on its location, an AVM can affect areas of the brain responsible for movement, sensation, speech, vision, memory, or coordination.
In some cases, an AVM can alter normal blood flow and potentially reduce the amount of blood reaching nearby brain tissue.
Large AVMs may put pressure on nearby tissues or cause changes in blood vessels and surrounding structures.
Seek emergency medical attention immediately if someone develops:
- A sudden, severe or unusual headache
- A seizure for the first time
- Sudden weakness or numbness
- Sudden difficulty speaking
- Sudden vision loss or major visual disturbance
- Severe confusion
- Loss of consciousness
- Sudden difficulty walking or maintaining balance
These symptoms may indicate bleeding or another serious neurological complication.
An AVM may be discovered after a person develops symptoms, or it may be found unexpectedly during imaging performed for another condition.
Doctors may use several tests to diagnose and evaluate an AVM.
A computed tomography (CT) scan can help identify bleeding in the brain and may provide information about an abnormal vascular structure.
Magnetic resonance imaging (MRI) provides detailed images of the brain and surrounding tissues. It can help identify an AVM and determine its location and relationship to nearby structures.
CT angiography uses contrast material to provide images of blood vessels and can help doctors evaluate the size and structure of an AVM.
Magnetic resonance angiography (MRA) can provide images of blood vessels without the need for conventional catheter angiography in some situations.
A cerebral angiogram is an important test for evaluating brain AVMs. A thin catheter is introduced into a blood vessel and contrast material is injected so that the blood vessels can be visualized using X-rays. Angiography can provide detailed information about:
- The arteries supplying the AVM
- The veins draining it
- The size and location of the AVM
- The pattern and speed of blood flow
- Features that may influence treatment
Treatment depends on several factors, including:
- Location of the AVM
- Size of the AVM
- Blood-flow characteristics
- Whether the AVM has previously bled
- The person’s age and general health
- Symptoms
- The risk associated with treatment
Some AVMs may be monitored rather than treated immediately, particularly when the risks of intervention are considered greater than the expected benefits. Treatment options may include surgery, endovascular embolization, stereotactic radiosurgery, or a combination of treatments.
In selected cases, a neurosurgeon may remove the AVM through an operation called surgical resection. Surgery may be considered when the AVM is located in an area that can be reached safely and the expected benefits outweigh the surgical risks.
During endovascular embolization, a catheter is guided through the blood vessels toward the AVM. A special substance is then used to reduce or block blood flow through the abnormal vessels. Embolization may sometimes be used as the main treatment, but it is also frequently used before surgery or radiosurgery to reduce blood flow to an AVM.
Stereotactic radiosurgery uses precisely focused radiation to target an AVM without making a traditional surgical incision. Over time, the radiation can cause the abnormal blood vessels to close. This treatment is particularly useful for some smaller AVMs or AVMs located in areas where conventional surgery would carry significant risks. The AVM does not disappear immediately after radiosurgery, and follow-up imaging is required to determine whether it has been completely closed.
In some people, doctors may recommend monitoring the AVM rather than immediately treating it. Regular follow-up and imaging may be recommended depending on the individual circumstances. The decision should be made with specialists experienced in treating vascular malformations.
Medicines cannot usually remove an AVM. However, medications may be prescribed to manage symptoms or complications. Depending on the individual’s condition, treatment may include medicines for:
- Seizure control
- Headache management
- Other neurological symptoms
People with a diagnosed AVM should discuss all medications, including over-the-counter medicines and supplements, with their healthcare professional.
There is currently no established way to prevent most AVMs because their exact cause is usually unknown.However, people who have been diagnosed with an AVM should follow their healthcare professional’s recommendations regarding monitoring, treatment, and management of associated conditions.
Living with an AVM can be different for each person. Some people remain symptom-free, while others require ongoing treatment and monitoring.
People diagnosed with an AVM should:
- Attend recommended follow-up appointments.
- Take prescribed medicines as directed.
- Report new or worsening neurological symptoms promptly.
- Discuss physical activity and other lifestyle questions with their doctor.
- Follow the specialist’s recommendations regarding imaging and treatment.
- Seek emergency care for sudden severe neurological symptoms.
An arteriovenous malformation is an abnormal connection between arteries and veins that bypasses the normal capillary network. AVMs can occur in different parts of the body and may sometimes cause bleeding or neurological symptoms.
Some AVMs cause no symptoms and may never cause serious problems. However, certain AVMs, particularly those in the brain, can rupture and cause potentially life-threatening bleeding. The risk varies depending on the AVM and the individual.
Yes. Headaches can occur in people with brain AVMs, although a headache does not necessarily mean that an AVM has ruptured. A sudden, extremely severe headache requires immediate medical evaluation.
Yes. Brain AVMs can irritate or affect surrounding brain tissue and may cause seizures.
Yes. Some AVMs can rupture and cause bleeding. A ruptured brain AVM can result in intracranial haemorrhage and requires emergency medical care.
Doctors may use CT scans, MRI, CT angiography, magnetic resonance angiography, and cerebral angiography to identify and evaluate an AVM.
Treatment may include surgical removal, endovascular embolization, stereotactic radiosurgery, or a combination of these approaches. In some cases, careful observation may be recommended.
No. The decision depends on the location, size, characteristics, symptoms, previous bleeding, overall health, and potential risks and benefits of treatment. A specialist should make the treatment recommendation after appropriate evaluation.
The possibility depends on the type of AVM and the treatment used. Follow-up imaging is important to determine whether an AVM has been completely eliminated and to monitor for recurrence or residual abnormal vessels.
Depending on its location and characteristics, treatment may involve a neurologist, neurosurgeon, interventional radiologist, vascular surgeon, or vascular medicine specialist. Complex AVMs are often managed by a multidisciplinary team.
Medical Disclaimer- This article is intended for general educational and informational purposes only. It should not be considered a substitute for professional medical advice, diagnosis, or treatment. Arteriovenous malformations can vary significantly from one person to another. If you have symptoms of an AVM, have been diagnosed with an AVM, or are concerned about your risk, consult a qualified healthcare professional for appropriate evaluation and treatment. Seek emergency medical attention immediately for sudden severe headache, seizure, loss of consciousness, sudden weakness or numbness, difficulty speaking, sudden vision problems, or other sudden neurological symptoms.
