Arteriovenous Malformations (AVMs)
An arteriovenous malformation (AVM) is an abnormal tangle of blood vessels in the brain in which arteries connect directly to veins. AVMs can cause bleeding, seizures, headaches, or neurological symptoms, and treatment depends on the AVM's location, anatomy, and individual risk of hemorrhage.
Quick Answer
An arteriovenous malformation (AVM) is a tangle of abnormal blood vessels where arteries connect directly to veins, bypassing the normal capillary system. AVMs can rupture and cause bleeding in the brain, although some are discovered before they cause symptoms. Treatment may involve microsurgery, endovascular embolization, stereotactic radiosurgery, or a combination of approaches based on the AVM’s anatomy, location, and individual bleeding risk.
Key Takeaways
- An AVM is a tangle where arteries connect directly to veins without normal capillaries.
- The main risk is bleeding into the brain, which can be serious.
- AVMs can also cause seizures and headaches, and some cause no symptoms.
- Treatment options include surgery, embolization, and radiosurgery.
- Not every AVM requires treatment; the decision weighs bleeding risk against treatment risk.
At a Glance
| What it is | Abnormal tangle connecting arteries directly to veins |
|---|---|
| Main risk | Bleeding (hemorrhage) in the brain |
| Other symptoms | Seizures, headaches, or none |
| Diagnosis | MRI, CT, and cerebral angiography |
| Treatment options | Microsurgery, embolization, stereotactic radiosurgery |
| Decision factors | Size, location, and bleeding risk versus treatment risk |
Symptoms
Many AVMs cause no symptoms and are found incidentally on imaging. When symptoms occur, the most serious is bleeding, which can present like a stroke with sudden headache, weakness, speech or vision changes, or loss of consciousness. Seizures are another common presentation, and some people experience headaches or focal neurological symptoms depending on the AVM’s location.
The symptoms and risks depend on the size and location of the AVM and whether it has bled. Because a first hemorrhage can be serious, understanding an individual AVM’s bleeding risk is central to deciding whether and how to treat it.
Common Warning Signs
- Seizures, especially new-onset in an adult
- Persistent or unusual headaches
- Focal weakness, numbness, or vision changes
- A pulsating sound in the head (rare)
- An AVM found incidentally on a scan
When to Seek Care Promptly
- Sudden severe headache (possible bleed): call emergency services
- Sudden weakness, numbness, or speech difficulty
- A first-time seizure
- Sudden vision loss
- Loss of consciousness
Diagnosis
AVMs are identified with MRI and CT, which show the malformation and any associated bleeding. Cerebral angiography, in which contrast is injected into the blood vessels and imaged, provides the detailed map of feeding arteries and draining veins that is essential for planning treatment.
The imaging characteristics, including size, location, and the pattern of drainage, are used to grade the AVM and estimate both its bleeding risk and the risk of each treatment option. This assessment guides the recommendation.
Treatment
AVM treatment is individualized. The goal is to reduce the risk of bleeding or eliminate the AVM when possible while balancing the risks of treatment based on the AVM’s size, location, anatomy, prior hemorrhage, and relationship to critical areas of the brain.
Microsurgical Resection
Microsurgery removes the AVM directly and can provide immediate elimination of the malformation when complete removal is achieved. It may be considered for AVMs that can be safely accessed without unacceptable risk to critical neurological function.
Endovascular Embolization
Embolization is performed from inside the blood vessels using a catheter to reach the arteries supplying the AVM. Embolic material is delivered to reduce or close abnormal blood flow. Embolization may be used before surgery or radiosurgery, as part of a combined treatment strategy, or in selected cases as the primary treatment.
Stereotactic Radiosurgery
Stereotactic radiosurgery delivers highly focused radiation to the AVM without an open operation. Over time, the treated blood vessels gradually close. It may be appropriate for selected small or deep AVMs that carry greater risk with open surgery.
A Combined Approach
Complex AVMs do not always fit a single treatment category. Some are best treated using a staged or combined strategy—for example, embolization followed by microsurgical removal or stereotactic radiosurgery.
Why treatment planning matters: The appropriate approach is determined after detailed imaging and review of both the AVM’s natural bleeding risk and the risks and benefits of each treatment option.
The Diagnosis-to-Treatment Pathway
1. Detection
An AVM may be found after a bleed, seizure, neurological symptoms, or incidentally on imaging.
2. Detailed imaging
MRI, CT, and cerebral angiography define the AVM's anatomy and blood flow.
3. Risk assessment
Size, location, drainage pattern, prior bleeding, and other features are evaluated.
4. Multidisciplinary treatment planning
Observation, microsurgery, embolization, radiosurgery, and combined approaches are considered.
5. Treatment
The selected treatment or staged combination of treatments is performed when appropriate.
6. Follow-up imaging
Imaging confirms treatment results and monitors the AVM over time.
Frequently Asked Questions
An arteriovenous malformation is a tangle of abnormal blood vessels in which arteries connect directly to veins without the normal capillary network in between. This creates high-pressure, fragile connections that can bleed. AVMs are usually present from birth, though they may not cause problems until later.
The main danger is bleeding into the brain, which can cause a stroke-like injury. The bleeding risk varies with the AVM’s size, location, and drainage pattern. Some AVMs also cause seizures. Assessing the individual bleeding risk is central to deciding whether treatment is warranted.
There are three main treatments, sometimes used in combination: microsurgical removal, endovascular embolization to close feeding vessels, and stereotactic radiosurgery to close the AVM gradually with focused radiation. The best approach depends on the size, location, and anatomy of the AVM.
No. For some AVMs, particularly large or deep ones in critical areas, the risk of treatment may exceed the risk of leaving it alone, so observation is chosen. The decision is individualized and made by weighing the bleeding risk against the risks of each treatment option.
Embolization is a catheter-based procedure that closes off the arteries feeding an AVM from inside the blood vessels, with no incision in the head. It is often used to shrink an AVM before microsurgery or radiosurgery, and occasionally as a standalone treatment for suitable lesions.
An AVM is a tangle of abnormal connections between arteries and veins, while an aneurysm is a balloon-like bulge in the wall of a single artery. Both can bleed, but they are different problems with different treatments. The two can occasionally occur together.
Specialists Who Treat Arteriovenous Malformations
Your care is provided by Atlantic Brain and Spine's neurovascular team, including fellowship-trained cerebrovascular and endovascular neurosurgeons.
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