What is a Brain AVM?

A brain arteriovenous malformation (AVM), also known as a cerebral AVM, is an abnormal tangle of blood vessels in which arteries connect directly to veins without the normal capillary network between them. Because blood flows through an AVM under higher pressure than normal, these abnormal blood vessels are more fragile and have an increased risk of bleeding.

Most brain AVMs are believed to develop before birth, although the exact cause remains unknown. They are usually not inherited and are rarely associated with a family history. A brain AVM is not a brain tumour and not cancer.

Some AVMs are discovered incidentally during brain imaging performed for another reason. Others present following bleeding into the brain (intracranial haemorrhage), seizures, headaches or, less commonly, neurological symptoms such as weakness, numbness or speech disturbance.

Although a diagnosis of a brain AVM can be unexpected and concerning, it is important to remember that not every AVM will bleed or require treatment. The challenge is determining which AVMs are likely to remain stable and which are most likely to benefit from intervention.

What Happens if a Brain AVM is Left Untreated?

One of the first questions following the diagnosis of a brain AVM is whether treatment is necessary.

The answer depends on the individual characteristics of the AVM together with the patient’s age, neurological condition, overall health and life expectancy.

Some AVMs remain stable for many years without causing problems, while others carry a significant lifetime risk of haemorrhage. Unlike many neurological conditions, the risk of bleeding persists throughout life unless the AVM is completely cured.

Current evidence suggests that the annual risk of haemorrhage from an untreated brain AVM is approximately 1–3% per year, although this varies considerably between patients.

Factors associated with a higher risk of bleeding include:

• Previous haemorrhage
• Deep location within the brain
• Deep venous drainage
• Associated brain aneurysms
• Venous outflow obstruction
• Pregnancy in selected patients

No single factor determines the risk of bleeding. Careful assessment of the AVM together with the patient’s neurological condition, overall health and long-term outlook is essential before deciding whether treatment is appropriate.

How is a Brain AVM Diagnosed?

Brain AVMs are usually identified on MRI or CT angiography. Comprehensive assessment often includes cerebral angiography (digital subtraction angiography, DSA), which remains the gold standard investigation.

Cerebral angiography provides detailed information about the arteries supplying the AVM, its internal architecture and pattern of venous drainage. This information is essential when determining whether observation, microsurgery, endovascular embolisation or stereotactic radiosurgery is the most appropriate treatment.

Do All Brain AVMs Need Treatment?

Not every brain AVM requires treatment.

For some patients, careful observation with regular MRI or angiographic surveillance provides the safest long-term strategy. For others, the lifetime risk of haemorrhage outweighs the risks associated with treatment.

The decision to intervene requires careful consideration of the AVM’s size, location, venous drainage, previous haemorrhage, associated aneurysms, patient age, neurological condition and overall health.

Every treatment recommendation should therefore be individualised.

What Are the Treatment Options?

Several treatment options are available, and many patients benefit from assessment by a multidisciplinary cerebrovascular team involving cerebrovascular neurosurgeons, interventional neuroradiologists and radiation oncologists.

Observation

Some AVMs can be managed safely with regular clinical review and imaging surveillance, particularly when the anticipated risks of treatment outweigh the potential benefits.

Microsurgical Resection

Microsurgical resection remains the only treatment capable of providing an immediate and definitive cure for a brain AVM.

Following complete removal, the future risk of haemorrhage is effectively eliminated. Unlike stereotactic radiosurgery, microsurgical excision provides immediate protection from future bleeding. Surgery is therefore recommended for carefully selected patients in whom the anticipated long-term benefits outweigh the operative risks.

Endovascular Embolisation

Endovascular embolisation involves passing a microcatheter through the blood vessels to inject specialised embolic material into the AVM.

This treatment is frequently performed before microsurgery or stereotactic radiosurgery to reduce blood flow through the AVM and improve treatment safety. In carefully selected small AVMs, embolisation alone may occasionally achieve complete obliteration.

Stereotactic Radiosurgery

Stereotactic radiosurgery (Gamma Knife or LINAC) uses highly focused radiation to gradually close the abnormal blood vessels.

Unlike surgery, obliteration occurs gradually over approximately two to three years, during which time the AVM continues to carry a risk of haemorrhage.

Which Treatment is Best?

There is no single treatment that is appropriate for every brain AVM.

The most appropriate treatment depends on the AVM’s size, location, pattern of venous drainage, previous haemorrhage, patient age, neurological condition and long-term goals.

Some AVMs are best managed with microsurgical resection, others with stereotactic radiosurgery, endovascular embolisation or a combination of these treatments, while some are safest managed with careful observation alone.

The goal is not simply to eliminate the AVM, but to recommend the treatment that offers the greatest long-term benefit while preserving neurological function and quality of life.

Why Seek an Early Specialist Opinion?

Every newly diagnosed brain AVM deserves expert assessment.

Early specialist review helps determine the individual risk of haemorrhage, explains the available treatment options and establishes whether observation or treatment is the most appropriate strategy.

Many patients benefit from discussion within a multidisciplinary cerebrovascular team, ensuring that every appropriate treatment option has been carefully considered before recommending the most suitable management plan.

Why Choose Professor Lai?

Brain arteriovenous malformations are uncommon and among the most technically demanding conditions treated in neurosurgery. Successful management requires careful assessment of the AVM, thoughtful treatment planning and expertise across the full spectrum of modern cerebrovascular care.

Professor Lai has performed more than 100 microsurgical brain AVM resections, including many complex lesions requiring advanced microsurgical techniques. His practice encompasses the assessment and management of both ruptured and unruptured brain AVMs, with treatment recommendations tailored to each patient’s individual circumstances.

Working within a multidisciplinary cerebrovascular team alongside interventional neuroradiologists and radiation oncologists, Professor Lai develops individualised treatment strategies that may include observation, microsurgical resection, endovascular embolisation, stereotactic radiosurgery or a combination of these approaches.

Patients are referred from across Melbourne, regional Victoria, throughout Australia and overseas, particularly for complex AVMs requiring specialised cerebrovascular expertise. Every recommendation is guided by sound clinical judgement, the best available evidence and a commitment to achieving the safest possible long-term outcome.

Frequently Asked Questions

Can a brain AVM disappear on its own?
No. Most brain AVMs persist throughout life unless successfully treated.

Does every brain AVM need treatment?
No. Many AVMs can be managed safely with careful observation. Treatment depends on balancing the natural risk of haemorrhage against the risks associated with intervention.

Can a brain AVM be cured?

Yes. Complete microsurgical removal provides an immediate and definitive cure. Selected AVMs may also be cured with stereotactic radiosurgery or, less commonly, endovascular embolisation, although these treatments are not appropriate for every AVM.

What is the best treatment for a brain AVM?
There is no single best treatment. Depending on the characteristics of the AVM, management may involve observation, microsurgical resection, endovascular embolisation, stereotactic radiosurgery or a combination of these treatments.

Can a brain AVM come back after surgery?
Following complete microsurgical removal confirmed by postoperative cerebral angiography, recurrence in adults is uncommon.

Can I exercise or fly if I have a brain AVM?
Most patients can continue their usual daily activities. Individual recommendations depend on the characteristics of the AVM, whether treatment is planned and your treating specialist’s advice.

Will I need long-term follow-up?

Some patients require ongoing MRI or cerebral angiographic surveillance, particularly if the AVM is managed conservatively or following stereotactic radiosurgery. Professor Lai will recommend an individualised follow-up plan based on your diagnosis and treatment.

Every brain AVM is unique. The most appropriate treatment depends not only on the AVM itself, but also on each patient’s individual circumstances, goals and long-term outlook. Careful assessment by an experienced cerebrovascular neurosurgeon is the first step towards understanding your individual risk and selecting the most appropriate management strategy.

Video