Kevin Lutz, MD, FACP
Dec 1 2019

A brain aneurysm is a weak or thin spot on a blood vessel in the brain that balloons or bulges out and fills with blood. It often looks like a berry hanging on a stem. Every brain aneurysm is unique in location, shape and size.

Brain HealthCirculatory System

A brain aneurysm is a weak or thin spot on a blood vessel in the brain that balloons or bulges out and fills with blood. It often looks like a berry hanging on a stem. Every brain aneurysm is unique in location, shape and size. The bulging aneurysm can put pressure on the nerves or brain tissue. A brain aneurysm can leak or rupture, causing bleeding into the brain (hemorrhagic stroke). A ruptured aneurysm quickly becomes life-threatening and requires prompt medical treatment.

Some brain aneurysms, particularly those that are very small, do not rupture, bleed or cause other problems. These types of aneurysms are usually incidentally detected during imaging tests for other medical conditions.  Brain aneurysms can occur anywhere in the brain, but most form in the major arteries along the base of the skull.

What causes Brain Aneurysms?

Certain risk factors for brain aneurysms are a result of conditions you have no control over, such as age or genetics. These include: 

  • Connective tissue disorders that can weaken artery walls.
  • Polycystic kidney disease: A condition that causes cysts to form on the kidneys.
  • Arteriovenous malformations: Tangled arteries that disrupt blood flow.
  • A family history of brain aneurysms: Having a first-degree family member (such as a parent, child, or sibling) who had a brain aneurysm increases your risk.
  • Age: Brain aneurysms are more common after age 40.

Other risk factors that you do have control over include: Untreated high blood-pressure, cigarette smoking and drug abuse, especially cocaine or amphetamines. These drugs raise blood pressure to dangerous levels. Less common, but still important, causes of brain aneurysms include head trauma, brain tumors, and infections in the walls of the arteries.

What are warning signs of Brain Aneurysms?

Unruptured Brain Aneurysms: Aneurysms typically start to cause symptoms when they are growing or when they are larger in size. Symptoms of an unruptured brain aneurysm include pain above and behind the eye, a dilated pupil in one eye, changes in vision or double vision, a droopy eyelid or numbness, weakness, or paralysis on one side of the body.

Ruptured Brain Aneurysms: All brain aneurysms can potentially rupture, causing blood to spill into the surrounding tissue. A rupture can lead to a hemorrhagic stroke, brain damage, coma, or death. Symptoms of a ruptured brain aneurysm include:

  • Sudden and very severe headache (the worst headache you have ever had)
  • Double vision
  • Nausea and vomiting
  • Stiff neck
  • Sensitivity to light
  • Seizures
  • Loss of conscious, either briefly or for a longer period of time
  • Cardiac arrest (heart attack)

How are Brain Aneurysms diagnosed?

A brain aneurysm may cause symptoms, as listed above. However, many times, they cause no symptoms at all. Because of this, doctors often are first alerted to a brain aneurysm through an imaging scan you might get for a completely different reason. 

The following tests are used to confirm a brain aneurysm diagnosis: Magnetic resonance angiogram (MRA) scan is a type of MRI that looks specifically at blood vessels. CTA, this is a special type of CT scan that focuses on the blood vessels. Angiogram: This is the gold standard for diagnosing brain aneurysms, offering precise details that help determine the best treatment. Aneurysms are also classified by size: small, large, and giant. Small aneurysms are less than 11mm in diameter (about the size of a large pencil eraser). Large aneurysms are 11mm to 25mm (about the width of a dime). Giant aneurysms are greater than 25mm in diameter (more than the width of a quarter).

How are Brain Aneurysms treated?

The best way to treat an aneurysm depends on many factors, such as the size, location, and shape of the aneurysm, age and overall health of the individual and medical and family history. For decades, the only treatment options for an aneurysm were clipping and coiling. Clipping is when a small metal clip is placed at the neck of the aneurysm to stop blood flow to it. Coiling is a minimally invasive treatment in which metal coils are placed in the bulge, causing a clot to form. The newest technique for treatment is flow diversion. This approach involves placement of a stent to block blood flow to the aneurysm. This causes a clot to form over time, while providing a scaffold for new blood vessels to grow. This eventually seals the aneurysm off from the main artery, essentially curing it.   

What is the prognosis of Brain Aneurysms?

An unruptured aneurysm may go unnoticed throughout a person's lifetime and not cause symptoms. However, after an aneurysm bursts, the person's prognosis largely depends on several factors, including: age, general health, preexisting neurological conditions, location of the aneurysm, extent of bleeding and time between rupture and medical attention. About 25% of individuals whose brain aneurysm has ruptured do not survive the first 24 hours and another 25% die from complications within 6 months. While some people may have permanent neurological damage, other individuals recover with little or no disability. Diagnosing and treating a brain aneurysm as soon as possible will help increase the chances of making a full recovery. Recovery from treatment or rupture may take weeks to months. 

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