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Neurology and Neurosurgery

A neurosurgeon explains arteriovenous malformations in the brain

Neurosurgeon discussing cerebral blood vessel x-ray image with a colleague. Arteriovenous malformations are a type of cerebrovascular condition.

08/11/2025

Learn about arteriovenous malformation causes, symptoms, diagnosis and treatment options for these abnormal blood vessels in the brain.

By Jon Lebovitz, MD, Chief of Neurointerventional Surgery at Vassar Brothers Medical Center, part of Northwell Health

Hearing you or a loved one might have an arteriovenous malformation (AVM) or experience symptoms from a rupture can be frightening and confusing. AVM is a rare and serious condition involving abnormal tangles of blood vessels that disrupt normal blood flow in the brain. They may cause no symptoms or lead to headaches, seizures or even life-threatening bleeding in the brain if they burst.

Knowing when to seek care is crucial. This guide explains brain AVM symptoms, causes, diagnosis and treatment options to help you understand this cerebrovascular condition.

Learn more about neurosurgery at the Nuvance Health Neuroscience Institute, now part of Northwell Health.

What is an arteriovenous malformation (AVM)?

An AVM is an abnormal connection between arteries and veins. AVMs most commonly form in the brain or spinal cord, although they can form anywhere in the body.

Normally, arteries and veins connect with capillaries to deliver blood and oxygen throughout the body. AVMs occur when arteries and veins connect to each other and bypass the normal capillary system.

This increases blood pressure in the arteries and veins, weakens the blood vessel walls and potentially can lead to a rupture. A ruptured AVM can cause hemorrhagic stroke (bleeding in the brain), which is a life-threatening medical emergency.

Key points about AVMs:

Rare and serious: Brain AVMs affect less than 1% of the population, but the risk of bleeding makes early diagnosis important.

Silent or symptomatic: Some AVMs remain silent for years or never cause symptoms. Others may cause headaches, seizures or stroke-like symptoms depending on their size and location in the brain.

Main risk is hemorrhage: A ruptured AVM can lead to life-threatening brain bleeding and long-term neurological damage.

How serious is an AVM?

AVMs can be life-threatening if they rupture and cause bleeding in the brain. The seriousness depends on the AVM’s size, location and whether bleeding has already occurred.

Risk of an AVM rupturing

AVMs have an estimated annual rupture risk of 1% to 3%. The risk can be higher if the AVM has an associated brain aneurysm or is located deep in the brain, like near the cerebellum or thalamus.

Survival odds after a ruptured AVM

About 85% to 95% of people survive a ruptured AVM if they get prompt neurosurgical treatment. Left untreated for too long, bleeding in the brain can cause long-term brain damage or death. Keep reading to know when to seek emergency care for signs of a ruptured AVM.

Side effects of a ruptured AVM

Lasting side effects from a ruptured AVM depend on where it was in the brain, how severe the bleeding was and how quickly it was treated.

Some people may experience stroke side effects, including weakness in their arms or legs, speech or vision changes, memory problems or other neurological deficits.

Side effects could be short- or long-term depending on the above-mentioned factors and individual baseline health. Early detection and treatment significantly improve the chances of avoiding severe, long-term or permanent complications.

Your brain’s ability to create new pathways and heal with the help of physical therapy, occupational therapy and speech therapy — especially from therapists who specialize in neuro rehab — can offer hope for people after a ruptured AVM.

Is AVM the same as a brain aneurysm?

No, an AVM is not the same as a brain aneurysm. While both involve abnormal blood vessels in the brain, they are distinct conditions:

AVM: A tangled cluster of arteries and veins that bypass capillaries, creating high-pressure fragile blood vessels.

Aneurysm: A balloon-like bulge in an artery wall that can rupture.

Sometimes, an AVM can form associated aneurysms, which further increase the risk of rupture and require careful monitoring.

Find a video about what happens if you have a brain aneurysm here.

What causes an AVM?

The exact causes of AVM are not fully understood, but most are believed to be congenital, meaning they form before birth. Here are a few reasons why AVMs form:

Developmental vascular anomalies: Errors during fetal development can lead to improper blood vessel formation.

Genetic conditions: Rare inherited disorders such as hereditary hemorrhagic telangiectasia (HHT), also called Osler-Weber-Rendu syndrome, can predispose people to AVMs.

Unknown triggers: Most AVMs appear without a clear family history or environmental cause.

Unlike aneurysms and strokes, other conditions and lifestyle factors such as high blood pressure and smoking don’t directly cause AVMs. However, diabetes, high blood pressure and smoking can cause damage to blood vessels and may increase the risk of complications from an AVM.

What are symptoms of an AVM?

Most AVMs don’t cause noticeable symptoms. Sometimes, AVMs are discovered incidentally when someone gets imaging of their head or neck for something else. Small AVMs that aren’t causing symptoms don’t usually need treatment. Keep reading to learn more about treatments for AVMs.

AVMs usually cause symptoms when they are large or after they rupture. Symptoms vary depending on the AVM’s size, location in the brain and whether bleeding has occurred.

Headaches, nausea and vomiting

AVMs can cause headaches before or after they rupture. Headaches before a rupture can range from mild pressure to severe, often localized to the side of the brain where the AVM is located.

Many people experience a sudden, severe headache after an AVM bursts. Called a thunderclap headache, people describe it as the worst headache of their life. Nausea and vomiting can also occur with this sudden headache due to the increased pressure in the brain.

Seizures

Seizures usually occur before the AVM bursts if the tangle of blood vessels put pressure on the brain and disrupt normal electrical activity.

Find a video about seizure first aid here.

Neurological changes

Weakness, numbness or tingling in the face, arms or legs may occur due to pressure on brain tissue from the AVM.

Vision or speech problems

AVMs near the visual cortex or language areas in the brain can cause blurry vision, double vision or difficulty speaking.

Difficulty with coordination, walking or dizziness

You may experience changes in your coordination, challenges walking or dizziness if the AVM affects the cerebellum. Dizziness is also associated with AVMs affecting the inner ear pathways.

How is an AVM diagnosed?

Diagnosis of AVM relies on imaging to visualize blood vessels and assess blood flow:

CT or MRI scans: Provide a detailed look at brain structures, identifies abnormal blood vessels and detects bleeding if present.

Cerebral angiography: An angiogram is considered the gold standard to diagnose an AVM. In a minimally invasive procedure, an endovascular neurosurgeon threads a catheter through an artery to reach the brain and takes X-rays to map the AVM’s size, shape and connections.

At Nuvance Health, neurosurgeons perform angiograms using a sophisticated biplane angiography system to get 3D, detailed images for more precise diagnostics and treatments. They also offer an advanced radial approach (accessing an artery at the wrist) to reach the brain resulting in faster recovery time for patients.

If you have non-emergent signs of an AVM, a good first step is usually seeking care from your primary care provider or a neurologist. They may order imaging and refer you to a neurosurgeon.

For emergent symptoms, like a thunderclap headache or seizure, call 911 to get to the nearest emergency department. When in doubt about what to do, go to the emergency department for an evaluation.

What are treatments for AVM?

Treatment is personalized based on the AVM’s size, location, rupture risk and the individual’s overall health. Treatments options include:

Observation: Small, low-risk AVMs may be monitored with regular imaging and neurological exams. Your neurosurgeon will assess the risk of bleeding.

Endovascular embolization: This is a minimally invasive procedure where a catheter delivers special materials (like coils or glue) to block abnormal blood flow and reduce rupture risk.

Microsurgical resection: Your neurosurgeon may recommend proactively removing the AVM during a microsurgical resection if it is accessible and poses a high rupture risk.

Stereotactic radiosurgery: This focused radiation gradually shrinks the AVM and may be recommended for small or hard-to-reach malformations.

Often, treatment involves a multimodal approach — for example, embolization followed by surgery or radiosurgery — to maximize safety and effectiveness.

At Nuvance Health, endovascular neurosurgeons are available 24/7 and use advanced imaging and surgical techniques to provide personalized treatment for AVM, prioritizing patient safety and long-term outcomes.

Find an endovascular neurosurgeon near me.

Can you recover from an AVM?

Recovery from an AVM depends on several factors, including rupture status, treatment type and location in the brain.

Unruptured AVMs: People treated before bleeding often recover fully and return to normal activities. Your neurosurgeon will assess the AVM’s bleeding risk and may recommend treatment to prevent it from rupturing.

Ruptured AVMs: Recovery is variable and may require rehabilitation. Physical, occupational and speech therapy can help restore function. Early intervention is key to lowering the risk of long-term disability or death from a ruptured AVM. Remember the above signs of an AVM and call 911 if you experience the worst headache of your life.

Ongoing care: Long-term follow-up care with imaging and neurological exams is important to ensure stability and address potential complications early.

Many people with AVMs can lead active lives after treatment, especially with a comprehensive care plan and regular follow-up.

The bottom line: Arteriovenous malformations are potentially life-threatening if not diagnosed and managed well. See your primary care provider or neurologist if you have signs of an AVM. They may order imaging and connect you with a neurosurgeon for further evaluation. If you experience a seizure or signs of ruptured AVM, like the worst headache of your life, call 911 for emergency medical services. Recognizing the signs and working with an experienced neurosurgeon are essential to prevent complications. With modern imaging, endovascular procedures and dedicated neuro rehabilitation care, many people can recover and resume their daily lives.