Why might an AVM require embolization in several sessions?
Why a cerebral AVM may be embolized in several sessions: size, feeding arteries, and its complementary role. What to ask your care team.
By Dr. Martin Roberto Casas MartínezOct 6, 20266 min read
In this article
- What is an AVM, and why does its structure affect the plan?
- What does embolization do, and how does it reach the brain?
- Why is it divided into several sessions?
- Is embolization complementary or the primary treatment?
- What happens between sessions, and when should I call 911?
- Frequently asked questions
- What should I ask the team about the staged plan?
- References
Summary: A cerebral AVM (arteriovenous malformation) may require embolization in several sessions because its structure—a tangle of vessels supplied by several arteries—cannot always be closed in a single procedure, and because embolization is often a complementary step before surgery or radiosurgery, rather than a complete treatment on its own. Each session has a specific goal, and the number of sessions is determined on a case-by-case basis.
When the team proposes dividing AVM embolization into more than one session, it is natural to wonder why it cannot all be done at once. Understanding why an AVM may require embolization in several sessions can help you understand the plan and speak clearly with the specialist. If you experience sudden neurological symptoms, call 911 before doing anything else.
What is an AVM, and why does its structure affect the plan?
A cerebral AVM is an abnormal connection between arteries and veins without the capillaries that normally separate them. Blood flows under high pressure through a tangle of vessels called a nidus, which may be supplied by several arteries and drain into different veins. This architecture determines how treatment is planned.
Capillaries are very small vessels that regulate blood flow. Because they are absent, an AVM carries a risk of bleeding. Its size, location, and number of feeding arteries vary greatly from person to person, so each AVM is evaluated with imaging of the blood vessels before deciding how to treat it.
What does embolization do, and how does it reach the brain?
Endovascular embolization is a minimally invasive procedure: a catheter (a thin, flexible tube) is guided from an artery in the groin or wrist to the vessels that supply the AVM, where a material is released to block blood flow. Its general goal is to reduce the risk of bleeding.
According to NINDS (the U.S. National Institute of Neurological Disorders and Stroke), embolization is often used as a complement to surgery or radiosurgery to reduce blood flow within the nidus, and is often incomplete or temporary on its own. This does not mean it has failed; rather, it is part of a broader strategy.
Why is it divided into several sessions?
It is divided into several sessions when the AVM is large or supplied by several arteries, so closing all the vessels in one procedure is not possible or advisable. Each session targets a group of vessels, and the team reviews the results before the next one.
- •Size and complexity of the nidus: With an AVM supplied by multiple arteries, treating all of them in one session would prolong the procedure and add risks.
- •Areas that remain open: Even with careful technique, parts of the nidus may remain unoccluded. An additional session allows them to be treated before moving on to the next phase of the plan.
- •Review between sessions: The interval allows the team to obtain updated imaging and adjust the strategy. A staged plan followed by surgery or radiosurgery is a recognized option.
The number of sessions is not set in advance: the specialist explains it and reviews it with you as the plan progresses.
Is embolization complementary or the primary treatment?
It depends on the individual AVM. Embolization is often complementary: it reduces blood flow within the nidus before surgery or radiosurgery. For some types of AVM, or when surgery is not possible, it may be the first option.
MedlinePlus notes that all three approaches—embolization, surgery, and radiosurgery (highly focused radiation that closes the vessels over time)—can be used together. Being complementary does not make embolization any less important.
Also, not all plans have the same goal: treatment aims to prevent complications by controlling bleeding and seizures and, when possible, eliminating the AVM. Ask which of these scenarios applies to your case.
What happens between sessions, and when should I call 911?
Between sessions, the team reviews imaging, assesses your neurological status, and plans the next stage. If you develop a severe or unusual headache, weakness, vision or speech problems, seizures, or any new neurological change during this time, call 911 or go to the emergency department immediately.
Do not wait for your next appointment or try to judge whether the symptom is “serious enough”: a partially treated AVM still carries a risk of bleeding. After emergency care, the team will decide how to proceed with the plan.
Frequently asked questions
How many embolization sessions will I need?
There is no set number. It depends on the size of the AVM, how many arteries supply it, its location, and whether embolization is performed before surgery or radiosurgery. The team reviews the results of each session before deciding on the next one.
If the first session went well, can I skip the remaining sessions?
Not without discussing it with the team. A partially embolized AVM still carries a risk of bleeding, and subsequent sessions or complementary treatment are part of the same plan. Any changes should be agreed on by you and the specialist, not decided on your own.
Can surgery or radiosurgery replace embolization?
Not necessarily: these approaches can be combined. Embolization often prepares the way by reducing blood flow, while surgery or radiosurgery aims to close the AVM. Which approaches are used, in what order, and whether they are combined depends on each case.
What should I ask the team about the staged plan?
If you experience sudden neurological symptoms, call 911 first. If it is not an emergency, these questions can help you understand the plan before or after each session:
- •What is the specific goal of this session: to reduce blood flow, prepare for surgery or radiosurgery, or treat a remaining area?
- •What imaging will be reviewed between sessions, and what will determine whether more or fewer sessions are needed?
- •What symptoms should I report right away, and what activities should I consider modifying while the plan is underway?
For non-urgent questions or to request an individual assessment, you can contact the office.
Informational notice: This content is for informational purposes and does not replace a medical consultation or constitute a diagnosis.
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