Aneurysm Fast Facts

An estimated 1 in 50 people have an unruptured brain aneurysm. That amounts to approximately 6.5 million Americans.

About 8 in every 10,000 people will suffer from a ruptured aneurysm each year.

As many as 80% of aneurysms never rupture.

Women are more likely to experience a ruptured aneurysm. African-Americans and Hispanics are at greater risk, as well.

About 500,000 people die each year as a result of a ruptured aneurysm. Half of the fatal cases are in people under the age of 50.

Two-thirds of people who survive a ruptured aneurysm will suffer from permanent neurological damage.

United Brain Association

About 500,000 people die each year as a result of a ruptured aneurysm. Half of the fatal cases are in people under the age of 50.

What is an Aneurysm?

A brain aneurysm (also called a cerebral aneurysm) is a bulge in a blood vessel in the brain caused by a weakening in a wall of the vessel. As blood pressure in the vessel pushes on the weak spot, the vessel wall expands outward like a balloon and is at risk of rupturing or leaking.

When an aneurysm ruptures or leaks, the result is bleeding into the surrounding brain tissue, an event called a hemorrhagic stroke. The bleeding commonly happens at the brain’s surface, between the brain tissue and the surrounding membranes. The bleeding can cause a damaging loss of oxygen to brain tissue. If fluid builds up in the space where the bleeding occurs, the resulting pressure on brain tissue can also cause damage.

The rupture or leakage of an aneurysm often occurs without warning, and it can quickly turn into a life-threatening situation. Immediate emergency treatment is vital to reduce the risk of permanent, severe neurological damage or death.

Symptoms of a Ruptured Aneurysm

Signs that an aneurysm has ruptured include:

  • Sudden, extreme headache (often described as well beyond any other kind of headache pain)
  • Nausea and/or vomiting
  • Light sensitivity and/or vision problems
  • Confusion
  • Drooping eyelid
  • Stiff neck
  • Seizure
  • Loss of consciousness

Sometimes an aneurysm leaks without fully rupturing. The most common symptom of a leaking aneurysm is a sudden, extreme headache. Very often, a leaking aneurysm will eventually rupture.

Unruptured Aneurysms

Many aneurysms don’t rupture. They don’t produce any symptoms and can go undetected. If an unruptured aneurysm is detected with imaging tests, treatment is most often recommended.

If a sizeable unruptured aneurysm puts pressure on brain tissue, it may cause symptoms including:

  • Pain near one eye
  • Vision problems
  • One dilated pupil
  • Numbness or tingling on one side of the face

What Causes an Aneurysm?

There is not an easily definable, predictable, or preventable cause of a brain aneurysm. Some aneurysms are present at birth, and others develop later in life due to inherited and/or external factors.

Risk factors for an aneurysm that are present at birth include:

  • Inherited connective tissue diseases such as Ehlers-Danlos syndrome. These conditions can make blood vessels unusually weak.
  • Inherited polycystic kidney disease. This condition causes cysts to form in the kidneys, and it also usually causes high blood pressure that can cause an aneurysm.
  • Arteriovenous malformation. This condition causes blood vessels to develop into tangles through which blood does not pass normally. When this happens in the brain, an aneurysm can result.
  • Family history. If a parent or sibling has suffered from an aneurysm, an individual is more likely to develop an aneurysm themselves.

Risk factors that may contribute to the development of an aneurysm later in life include:

  • Smoking
  • High blood pressure
  • Substance abuse

Is an Aneurysm Hereditary?

Many aneurysms are probably caused by factors that are not connected to inherited traits. However, some aneurysms are almost certainly the result of inherited risk factors. A few inherited diseases (Ehlers-Danlos syndrome, polycystic kidney disease, etc.) increase the risk of developing an aneurysm because they produce the conditions favorable for developing the problem.

Aside from these relatively easy-to-spot inherited conditions, a family history of aneurysms also increases the risk of aneurysm development in general. This connection suggests that a genetic predisposition may be to blame, but researchers have not yet been able to find a definite genetic cause.

How is an Aneurysm Detected?

When a brain aneurysm ruptures or leaks, life-threatening complications can set in within minutes. The patient must receive emergency medical treatment immediately. If someone near you experiences a sudden, extreme, unexplained headache, has a seizure, or loses consciousness, call 911 or your local emergency medical number immediately.

If an unruptured aneurysm is detected with an imaging exam, your doctor may suggest treatment to prevent a rupture from happening in the future.

Imaging scans are generally not used to screen for brain aneurysms in healthy patients. However, some doctors may recommend screening for people who have a family history of aneurysms or who have a medical condition that increases the risk of an aneurysm.

How is an Aneurysm Diagnosed?

If a patient shows symptoms consistent with a ruptured aneurysm, doctors will perform a series of tests to confirm bleeding in the brain. Tests may also be conducted if the symptoms suggest the presence of an unruptured aneurysm.

Diagnostic tests for an aneurysm include:

  • Imaging exams. Computerized tomography (CT) and magnetic resonance imaging (MRI) scans will show doctors what’s happening in your brain and can reveal the presence of an aneurysm or bleeding.
  • Spinal tap. An examination of the fluid from your spinal column can indicate that a type of bleeding called a subarachnoid hemorrhage has occurred. This test may be able to detect an aneurysm even if it is not currently bleeding.
  • Cerebral angiogram. This test uses a thin tube to inject dye into an artery. The dye, which is visible on x-rays, then travels to the brain; it can indicate the presence of an aneurysm. This test is usually used when other tests are inconclusive.


How is an Aneurysm Treated?

Treatment for a ruptured aneurysm is usually surgical and aimed at stopping blood flow into the aneurysm. Some surgical treatments are more invasive than others.

  • Surgical clipping. This procedure uses a small wire clip that closes off the aneurysm and stops blood from flowing into it. The surgery requires the opening of the patient’s skull and carries its own risks.
  • Endovascular coiling. This procedure uses a small metal coil to close off the aneurysm. The coil is inserted into an artery (usually in the groin) through a small tube, and the coil is guided through the body to the site of the aneurysm. This surgery is less invasive and less risky than surgical clipping.
  • Flow diverters. This procedure uses small tubes inserted into blood vessels to divert blood flow away from the aneurysm. This procedure may be used to treat large aneurysms that other methods can’t directly address.

These procedures may be employed to treat unruptured aneurysms, but sometimes the surgery’s risks are considered to be greater than the risk of the aneurysm itself.

Medications may also be used to treat symptoms and complications following a non-fatal aneurysm rupture.

How Does an Aneurysm Progress?

A brain aneurysm rupture is typically a sudden, quick event that produces profound damage. A quarter of people who suffer a ruptured aneurysm die within 24 hours. Another quarter of patients die from complications within six months. Those who survive often experience severe neurological damage that affects them for the rest of their lives. Some, however, recover with few significant lasting effects.

Even when a ruptured aneurysm is not immediately fatal, the event’s complications can be life-threatening in the future. These complications include:

  • New bleeding. A ruptured aneurysm usually only bleeds for a few seconds. If the patient survives, however, an untreated aneurysm is likely to rupture or bleed again.
  • Fluid build-up. When an aneurysm disrupts blood flow in the brain, the result can be the build-up of cerebrospinal fluid around the brain. This fluid build-up can deprive the brain of oxygen and cause tissue damage. This complication can lead to neurological injury or death.
  • Sodium imbalance. Aneurysm bleeding can cause low sodium levels in the brain; a condition called hyponatremia. This can cause damaging swelling of the brain.
  • Vasospasm. This is a narrowing of blood vessels in the brain caused by the aneurysm rupture. The resulting low blood flow can deprive brain tissue of oxygen and cause damage.

How is an Aneurysm Prevented?

Avoiding certain lifestyle risk factors may decrease the chance that you’ll develop a brain aneurysm or that an unruptured aneurysm will rupture. Avoiding these risk factors is especially important if you have a family history of aneurysms.

Avoidable risk factors include:

  • Smoking
  • Excessive alcohol consumption
  • Drug use
  • Poor diet
  • Lack of exercise

Aneurysm Caregiver Tips

  • Be aware of the warning signs of a ruptured aneurysm. Immediate treatment is the key to your loved one’s survival. An excruciating, unexplained headache is a symptom of a ruptured or leaking aneurysm. When it occurs, seek emergency medical help immediately.
  • Be prepared for a long recovery. Survivors of a ruptured aneurysm usually face a lengthy rehabilitation process filled with hard work and setbacks. Keep recovery goals small and achievable, and celebrate victories as they come.

Many people with aneurysms also suffer from other brain and mental health-related issues, a condition called co-morbidity. Here are a few of the disorders commonly associated with aneurysms:

Aneurysm Brain Science

Scientists are trying to find ways to spot aneurysms that are likely to rupture and find ways to treat aneurysms to prevent their rupture. Research is also ongoing into genetic, physiological, and environmental risk factors with the hope of finding treatments that may prevent the development of aneurysms.

Areas of current research include:

  • Genetics. Scientists have identified a connection between brain aneurysms and aneurysms in the aorta (the main artery leading from the heart to the rest of the body). Recent studies have suggested a genetic trait that seems to increase the risk for both kinds of aneurysms. The implication is that those with a family history of aortic aneurysms should also be alert to an increased risk of a brain aneurysm.
  • Diagnosis. Researchers are examining a common type of brain aneurysm and determining which features of the aneurysm cause the most significant risk of rupture. Their data can be used to develop a diagnostic scale that could, in turn, determine if the risks of surgical treatment are justified.
  • Medication. The anti-inflammatory effects of aspirin have been shown to decrease the risk of aneurysm rupture. However, aspirin can also cause excessive bleeding, an effect that is dangerous if the aneurysm ruptures. Researchers have been working to find effective anti-inflammatory medications that don’t pose the same bleeding risks.
  • Hormones. Women are more likely to experience brain aneurysms than men, especially after menopause. Therapies that replace estrogen, a hormone whose level declines in women after menopause, decrease the risk of a type of aneurysm rupture called a subarachnoid hemorrhage. Research is ongoing into how, exactly, estrogen guards against aneurysm rupture.

Aneurysm Research

Title: Aneurysmal Subarachnoid Hemorrhage Trial RandOmizing Heparin (ASTROH)

Stage: Recruiting

Principal investigator: Kevin N Sheth, MD 

Yale University

New Haven, CT

This study’s primary objective is to investigate the safety and clinical effect of a continuous low-dose intravenous unfractionated heparin (LDIVH) infusion to prevent aneurysmal subarachnoid hemorrhage (aSAH) induced neurocognitive dysfunction and other delayed neurological deficits.

Additionally, increased blood and CSF levels of specific inflammatory biomarkers (IL-6, hsCRP, etc.) have been correlated to aSAH patients with poor clinical outcomes. Unfractionated heparin (UFH) has known anti-inflammatory actions. As a result, this study’s secondary objective will be to evaluate whether LDIVH can reduce blood and CSF inflammatory biomarkers levels compared to controls and whether there is an association between inflammatory biomarker levels and cognitive outcomes in aSAH.


Title: Study to Evaluate Cerebral AneurysmFlow Results in Occlusion (CARO)

Stage: Recruiting

Principal investigator: Ricardo Hanel, MD, PhD 

Baptist Medical Center Jacksonville

Jacksonville, FL

AneurysmFlow R1.0 is an approved (i.e., CE labeled, 510k, Health Canada) software tool intended to provide relevant information on the blood flow in a cerebral aneurysm and its parent artery based on angiography. It calculates the Mean Aneurysm Flow Amplitude (MAFA) ratio to measure the volumetric flow rate quotient before and after Flow Diverter Stent (FDS) implantation in the region of interest.

The current study is a prospective, single-arm, observational, multicenter cohort study to assess the MAFA ratio’s predictive value for predicting full aneurysm occlusion 12 months after flow diverter placement.


Title: Framing Eighteen Coils in Cerebral Aneurysms Trial (FEAT)

Stage: Recruiting

Principal investigator: J D Mocco, MD, MS 

Icahn School of Medicine at Mount Sinai

New York, NY

Primary Study Objective: Occlusion rate: angiographic occlusion, improvement or no change in the aneurysm’s post-coiling appearance as judged by an independent core lab on follow-up angiography at 12-18 months after endovascular embolization.

Secondary Objectives:

Treatment-related morbidity and mortality, as measured by the NIH stroke scale.

Packing density as measured by volumetric filling of the aneurysm.

Clinical outcome at 3-6 and 12-18 months post-coiling, as measured by the modified Rankin scale.

Re-hemorrhage and re-treatment rates.

Study Design: FEAT will be a prospective, randomized trial comparing the utilization of 0.014-0.0155″ coils versus smaller diameter coils in mid-sized aneurysm treatment. The 0.014-0.0155″ bare platinum coils (Stryker, Natick, MA) are FDA-approved and in common use at institutions in this country and across the world. Patients will be enrolled who meet the inclusion criteria and consent to participate. A central web-based system will randomly assign patients in a 1:1 manner to either the framing coil treatment or the non-framing coil treatment. Data on each patient will be collected at the time of enrollment and treatment and at first and second follow-up visits.

You Are Not Alone

For you or a loved one to be diagnosed with a brain or mental health-related illness or disorder is overwhelming, and leads to a quest for support and answers to important questions. UBA has built a safe, caring and compassionate community for you to share your journey, connect with others in similar situations, learn about breakthroughs, and to simply find comfort.

United Brain Association

Make a Donation, Make a Difference

We have a close relationship with researchers working on an array of brain and mental health-related issues and disorders.  We keep abreast with cutting-edge research projects and fund those with the greatest insight and promise.  Please donate generously today; help make a difference for your loved ones, now and in their future.                                                                 

The United Brain Association – No Mind Left Behind

Share Your Story

If you have an experience, a story, or someone in your life you want to recognize for their strength and willpower, please share it with us. We want to hear from you because listening is part of healing.

Connect With Us

Receive news on Brain Awareness, the Latest Research, and Personal Stories