Cerebral Aneurysms

What is a cerebral aneurysm?

A cerebral aneurysm (or brain aneurysm) is a weak spot on an artery in the brain that balloons and fills with blood. An aneurysm can put pressure on the brain tissue and nerves.

An aneurysm can also burst open (or rupture) and release blood into the brain or surrounding area (called a hemorrhage). All aneurysms have the potential to rupture and hemorrhage. A ruptured aneurysm can cause serious health problems such as stroke, brain damage, coma, and even death.

Some aneurysms, especially very small ones, do not bleed or cause other problems. These aneurysms are usually discovered during imaging tests for other medical issues. Aneurysms can occur anywhere in the brain, but most form in the major arteries along the base of the skull.

Depending on the aneurysm, doctors may treat it with surgery, procedures, medications, or by monitoring it over time.

Symptoms of cerebral aneurysms

Unruptured, ruptured, and leaking aneurysms can have different symptoms.

If you experience a sudden, severe headache, especially with any other symptoms, call 911 and seek immediate medical attention.

Types of cerebral aneurysms

There are three types of cerebral aneurysms:

• Saccular aneurysm: Also known as a “berry aneurysm,” this aneurysm has a rounded blood-filled sac. Saccular aneurysms are the most common type and happen most often in adults. The sacs are usually on arteries at the base of the brain.
• Fusiform aneurysm: An aneurysm that balloons or bulges out on all sides of the artery.
• Mycotic aneurysm: An aneurysm caused by an infection that weakens the arteries in the brain. The infection weakens the artery wall, causing a bulging aneurysm to form.

Aneurysms are also classified by size—small, large, and giant.

• Small: An aneurysm less than 11 millimeters in diameter (about the size of a large pencil eraser).
• Large: An aneurysm 11 to 25 millimeters in diameter (about the width of a dime).
• Giant: An aneurysm greater than 25 millimeters in diameter (more than the width of a quarter).

Who is more likely to get a cerebral aneurysm?

Brain aneurysms can occur in anyone and at any age. Sometimes, aneurysms may be present from birth, usually because of a problem in an artery wall.

Risk factors for developing an aneurysm

A risk factor is a condition or behavior, like high blood pressure or smoking, that increases the likelihood of having a certain health problem compared to those who don’t have the risk factor. Having a risk factor doesn’t mean a person will have an aneurysm, and not having a risk factor doesn’t mean they won’t.

Sometimes cerebral aneurysms are the result of genetics, medical issues, behaviors, and other risk factors such as:

Less common risk factors include artery wall infections caused by injecting drugs into the veins, head trauma and injuries, and brain tumors.

Risk factors for a brain aneurysm rupture

Not all cerebral aneurysms will rupture. In addition to high blood pressure and smoking, there are certain risk factors that can affect the risk of rupture:

• Growth. Aneurysms that grow, even if they are small, are the biggest risk for rupture (followed by size).
• Size. The largest aneurysms are most likely to rupture in a person who did not show symptoms before the rupture.
• Previous ruptures. Having had a previous rupture or sentinel bleed increases risk for future ruptures.
• Location. Aneurysms located in certain parts of the brain have a higher risk of rupturing. These include aneurysms on a pair of arteries in the back of the brain, and possibly those on a single artery in the front of the brain.
• Family history. A family history of aneurysm rupture may mean a higher risk of rupture for a person with an aneurysm.

How are cerebral aneurysms diagnosed and treated?

Diagnosing cerebral aneurysms

Most people don’t notice cerebral aneurysms until they rupture or are discovered during medical imaging tests for another medical issue.

If a person has a severe headache or any other symptoms seen with a ruptured aneurysm, a doctor will order tests to determine if blood leaked into the space between the skull and brain.

There are several tests doctors can use to diagnose brain aneurysms and help determine the best treatment. These include:

• CT (computed tomography) scans: This is often the first test a doctor orders to find out if blood leaked into the brain. CT angiography uses a contrast dye injected before the scan to show the aneurysm’s size, location, and shape.
• Cerebral angiography: This imaging technique can find blocked or weak spots in arteries in the brain or neck. The test can find the exact location, size, and shape of an aneurysm. A doctor passes a catheter (a long, flexible tube), usually from the groin arteries, up to the brain, and injects a small amount of contrast dye into the neck and brain arteries.
• MRI (magnetic resonance imaging) scans: Magnetic resonance angiography MRI is an imaging technique that uses a strong magnetic field and radio waves to create detailed images of blood vessels and can look for aneurysms in the brain that have not ruptured. This MRI produces detailed images of the brain arteries to show the aneurysm’s size, location, and shape.
• Cerebrospinal fluid (CSF) analysis: This test uses cerebrospinal fluid (CSF), which cushions and protects the brain and spinal cord, to help find bleeding around the brain. A doctor usually collects the CSF by performing a spinal tap (also called a lumbar puncture). If bleeding is found, the person will need additional tests to identify the cause.

Learn more about neurological diagnostic tests and procedures.

Treating cerebral aneurysms

Not all cerebral aneurysms need treatment. A doctor may recommend monitoring the growth of very small unruptured aneurysms, as long as there are no issues that may increase the risk of rupture. People with unruptured aneurysms should aggressively treat any other medical issues that increase rupture risk, including high blood pressure. They should also make a plan to quit smoking or using drugs like cocaine.

Serious medical issues can result from treating unruptured aneurysms without symptoms. A doctor will consider the chance of rupture when deciding whether to treat an unruptured aneurysm without symptoms. Other factors include the person’s age, health, and family and medical history.

Surgery, endovascular treatments, or other therapies are often recommended to manage symptoms and prevent damage from unruptured and ruptured aneurysms.

What are the latest updates on cerebral aneurysms?

NINDS, part of the National Institutes of Health (NIH), is the leading federal funder of research on the brain and nervous system, including research on cerebral aneurysms. NINDS supports new and innovative research to better understand, diagnose, and treat cerebral aneurysms.

NINDS-supported research projects cover a wide range of topics on cerebral aneurysms. This includes research on:

• How gene changes affect aneurysm formation
• Using computational and statistical models to predict aneurysm growth and rupture
• Improving current treatments to help people with aneurysms have better health outcomes

Genetics

Having family members with aneurysms can increase a person’s risk of getting one. Researchers are working to understand the specifics of aneurysm risk within families, such as how gene variations can affect blood vessels and aneurysm formation. They are also looking to identify aneurysm-related genes.

Aneurysms in the brain and aneurysms in the largest artery in the body (called the aorta, which begins in the heart) share biological functions. Genome-wide association studies (GWAS) show that a specific location on chromosome 9p21 increases the risk of aneurysms in the brain and the aorta. This GWAS data, combined with other genetic and DNA data, show that individuals and families with one type of aneurysm may be at increased risk of the other. Genetics research can improve diagnosis options for people with this increased risk and help us better understand the impact on the body when aneurysms form and rupture.

Diagnostic tools

Many studies supported by NINDS focus on improving the ways to detect and treat aneurysms. Some recent and ongoing studies on new tools and predictive models include:

• Creating a statistical and computational system to predict the growth of unruptured intracranial aneurysms (UIA) over 24 months and their growth patterns over five years. This system can help doctors make treatment decisions, determine the risk of rupture, and develop personal monitoring plans for people with UIA.
• Identifying the common traits of ruptured aneurysms to guide treatment and the development of computational models. These models can predict similar traits in unruptured aneurysms and help doctors figure out rupture risk.
• Developing a new noninvasive optical tool (called pathlength resolved diffuse correlation spectroscopy) to study how stroke damage happens in people with subarachnoid hemorrhage.
• Generating ways to diagnose brain aneurysms based on molecules that predict a high risk of rupture. This procedure uses brain imaging and does not require the skull to be opened. This less invasive tool would also allow an affected person to get treated before an aneurysm ruptures.
• One of the biggest research efforts in the subarachnoid hemorrhage (SAH) field is trying to develop an imaging technique or biomarker to predict who will develop DCI.

Hormone replacement therapy

Aneurysms and subarachnoid hemorrhage are more common in postmenopausal women than in men. Estrogen replacement therapy reduces the risk of subarachnoid hemorrhage in postmenopausal women. Researchers supported by NINDS are investigating how estrogen protects women from developing aneurysms. They predict it mostly occurs through inflammatory cells, but are doing more studies to support this theory.

Devices and medications

NINDS-funded scientists are discovering new ways to treat severe headaches caused by subarachnoid hemorrhage without the use of opioids—which can cause addiction and have dangerous side effects. They are exploring the use of a nerve-blocking procedure that has been successful in treating migraines. Scientists are also using mouse models to find out how aspirin protects the brain from aneurysms, and how inflammation impacts how aneurysms form and rupture.

NINDS research is exploring ways to make treatment better for people with aneurysms, such as improving flow diverters used for aneurysm treatment. This may lead to better blood vessel repair and reduce the risk of stroke or brain hemorrhage. They are exploring the use of different coils and other materials to block blood flow into aneurysms, and seeking to better understand how blood flow speed and pressure can affect whether or not aneurysm treatment works. Scientists are also studying how a specific medication, called Sirolimus, affects unruptured aneurysms during surgery and other treatments.

For more information on research about cerebral aneurysms, check NIH RePORTER, a searchable database of current and past research projects funded by NIH and other federal agencies. RePORTER also has links to publications and resources from these projects.

For research articles and summaries on cerebral aneurysms, search PubMed, which contains citations from medical journals and other sites.

How can I or my loved one improve care for people with cerebral aneurysms?

Consider participating in a clinical trial so clinicians and scientists can learn more about cerebral aneurysms and related disorders. Clinical research with human participants helps researchers learn more about a disorder and perhaps find better ways to safely detect, treat, or prevent disease.

All types of participants are needed—those who are healthy or may have an illness or disease—of all different ages, sexes, races, and ethnicities. This helps to ensure that study results apply to as many people as possible, and that treatments will be safe and effective for everyone who will use them.

For information about participating in clinical research, visit the NINDS Clinical Trials siteand NIH Clinical Research Trials and You. Learn about clinical trials currently looking for people with cerebral aneurysms at ClinicalTrials.gov, a searchable database of current and past clinical studies and research results.