What tests show how blood flows through a cerebral AVM?
What CT, MRI, MR angiography, and cerebral angiography show about blood flow through an AVM, and why it’s helpful to bring previous imaging studies.
By Dr. Martin Roberto Casas MartínezSep 11, 20266 min read
In this article
- What does the specialist need to know about blood flow through an AVM?
- What do CT and MRI show?
- What do MR angiography and CT angiography show?
- Why is cerebral angiography ordered?
- Should the specialist review my previous test results?
- Frequently asked questions
- What should you ask the specialist about your tests?
- References
Summary: Cerebral angiography is the test that most precisely shows how blood flows through a brain AVM: which arteries supply it, how blood passes through the nidus, and which veins drain it. CT, MRI, and MR angiography provide complementary information, and the specialist decides which test is needed based on what is already known about each case.
Knowing which tests show how blood flows through a brain AVM helps explain why the specialist reviews your images and sometimes requests additional tests. An arteriovenous malformation (AVM) is an abnormal connection between arteries and veins in the brain; assessing it involves more than confirming that it exists—it also means understanding how blood flows through it.
If you suddenly develop a very severe headache, a seizure, weakness, or difficulty speaking, call 911 before continuing to read.
What does the specialist need to know about blood flow through an AVM?
The specialist needs to know where the AVM is, how large it is, which arteries supply it, which veins drain it, and how blood flows through it. No single test answers all these questions, so tests are sometimes combined.
According to NINDS (the U.S. National Institute of Neurological Disorders and Stroke), in an AVM, blood flows directly from the arteries to the veins without passing through the capillaries, the tiny vessels that deliver oxygen to tissue. This tangle of abnormal blood vessels is called the nidus. Its location in relation to areas that control language, movement, or vision, along with certain features of its blood vessels, helps guide the options that will be discussed.
What do CT and MRI show?
CT and MRI are usually the first tests. CT is especially useful for detecting bleeding, while MRI shows the AVM’s location and its relationship to the surrounding brain tissue in greater detail.
Computed tomography (CT) uses X-rays and can be performed in just a few minutes, so it is often used in emergency situations. Magnetic resonance imaging (MRI) uses a magnetic field and provides detailed images of the brain, which are useful for locating the lesion in relation to nearby structures. However, neither test fully describes the path of blood through the nidus.
What do MR angiography and CT angiography show?
MR angiography and CT angiography show blood vessels without inserting a catheter. The NINDS notes that MR angiography can record the pattern and speed of blood flow through the lesion.
Magnetic resonance angiography (MRA) is an MRI focused on the blood vessels; CT angiography is a CT scan performed with contrast dye (a substance that makes blood vessels stand out) injected into a vein. MedlinePlus includes them among the tests used to diagnose an AVM. They can show the arteries supplying the malformation and the veins draining it. The specialist assesses whether this information is enough for your case or whether a more detailed test is needed.
Why is cerebral angiography ordered?
Cerebral angiography is ordered because, according to the NINDS, it provides the most precise images of the structure of blood vessels in an AVM. It shows, in sequence, how blood enters the nidus, passes through it, and exits.
MedlinePlus explains that a catheter (a thin tube) is inserted into an artery, usually in the groin or wrist, and advanced to the arteries in the neck. Contrast dye is then injected while X-rays are taken. Fleni, a neurological center in Argentina, notes that the test provides information about the AVM’s location, shape, size, dynamic behavior, and risk factors for rupture. It is an invasive procedure with its own risks, so it is not automatically recommended for everyone with an AVM.
Should the specialist review my previous test results?
Yes. Reviewing previous test results helps determine which questions have already been answered, compare the AVM over time, and avoid unnecessary repeat tests. That is why it is helpful to bring the complete images, not just the written report.
The report describes what the radiologist observed; images on a disc or in digital format allow the specialist to review them directly. Gather the studies, along with their dates and where they were performed, as well as a summary of your symptoms and a list of the medications you take. With this information, the care team can decide whether the available information is enough or whether an additional test is needed, and explain what it will be used for.
Frequently asked questions
What are the risks of cerebral angiography?
Like any invasive procedure, it carries risks. MedlinePlus lists an allergic reaction to the contrast dye, bleeding or a blood clot where the catheter is inserted, kidney damage from the contrast dye, and, rarely, damage to an artery that causes a stroke. The specialist explains the risks and benefits in your case.
Can transcranial Doppler be used to evaluate an AVM?
It may provide complementary information. The NINDS notes that this ultrasound of the arteries in the brain can help detect medium or large AVMs and bleeding, but it does not replace tests that show the structure of the nidus. Its use depends on each case.
Can a test tell whether an AVM will bleed?
Not with certainty. Tests show features that the specialist considers when assessing the risk of bleeding, but none can reliably predict what will happen. This information is considered along with your symptoms and medical history to assess the options with you.
What should you ask the specialist about your tests?
If you have a sudden, severe headache, a seizure, weakness, or difficulty speaking, call 911 before anything else. For your appointment, these questions may help:
- •Are the tests I already have enough to understand how blood flows through my AVM?
- •If an additional test is needed, what information will it provide, and what risks does it carry?
- •Which features of my AVM are most important in deciding how to manage it?
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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