What Is a Brain Aneurysm?

What Is a Brain Aneurysm?

A brain aneurysm, also called a cerebral aneurysm, is a bulge in the wall of an artery in the brain. If it ruptures, it can cause a stroke and can be life-threatening as bleeding in the brain occurs. NewYork-Presbyterian’s neurologists, neurosurgeons, neurocritical care specialists, and neuroradiologists are experts in diagnosing and treating brain aneurysms.

What Causes a Brain Aneurysm to Rupture?

Just as a weakness in the sidewall of a tire can get worse over time and lead to a blowout, cerebral aneurysms can continue to weaken the artery’s wall and eventually lead to a rupture. But not all aneurysms will rupture. Several factors may increase the chance of a brain aneurysm rupturing:

  • Smoking
  • High blood pressure, which damages and weakens the arteries
  • Size, with larger aneurysms and those that continue to grow at the greatest risk of a rupture
  • Family history of ruptured aneurysm
  • Personal history of multiple brain aneurysms and prior aneurysm rupture

Types of Brain Aneurysms


An aneurysm begins with a weakness in the three-layered artery wall. Blood flowing past the weak spot puts pressure on it and causes the artery to bulge and swell. There are several types of brain aneurysms:

  • A saccular aneurysm (also called a berry aneurysm) has a narrow stem with a round berry-shaped bulge. About 90 percent of brain aneurysms are saccular aneurysms.
  • A fusiform aneurysm bulges out on all sides, creating the appearance of a dilated blood vessel rather than a sac protruding from an artery. These are the aneurysms most often associated with atherosclerosis, a buildup of arterial plaque.
  • A dissecting aneurysm starts with a tear in the inner wall of the artery, which causes blood to leak into the area between the other layers.

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Signs & Symptoms of Brain Aneurysm


Brain aneurysm symptoms may vary depending on whether the aneurysm has ruptured.

Unruptured brain aneurysm symptoms

The majority of unruptured aneurysms are asymptomatic. However, they may cause you to experience:

  • Double vision or other vision changes
  • Headache or pain above and behind an eye
  • Weakness
  • Numbness
  • A dilated pupil in the eye
  • Weakness on one side of the face

Symptoms of a ruptured brain aneurysm

When an aneurysm ruptures, it may cause other symptoms:

  • A severe headache, often described as the “worst headache of one’s life”
  • Nausea and vomiting
  • Double vision
  • Stiff neck
  • Light sensitivity
  • Loss of consciousness
  • Seizures

A ruptured aneurysm is an emergency and can be fatal.

What Causes a Brain Aneurysm?


Aneurysms typically form at branch points in arteries because these sections are the weakest. Over time, wear and tear in the blood vessel wall can cause this weakness.

Risk Factors for Brain Aneurysms

Risk Factors

There are several risk factors for developing a brain aneurysm, some controllable and others uncontrollable. These include:

  • Smoking
  • High blood pressure
  • Diabetes
  • High blood cholesterol
  • Drug use, especially cocaine or amphetamines, which raise blood pressure, and intravenous drug use, which can cause infection-related aneurysms
  • Inherited risk factors such as connective tissue disorders, polycystic kidney disease, arteriovenous malformations (tangles of blood vessels in the brain), and a family history of aneurysm in a parent, sibling, or child

How to Prevent Brain Aneurysms


While some risk factors for aneurysms, such as heredity, cannot be controlled, there are other steps you can take to reduce your risk of developing a brain aneurysm or to lower the risk of rupture if you already have one:

  • Avoid smoking
  • Get regular physical activity
  • Follow a healthy diet high in fruits and vegetables and low in fat and cholesterol
  • If you drink alcohol, do so in moderation
  • Avoid using recreational drugs such as cocaine, amphetamines, and intravenous drugs
  • Keep high blood pressure under control by taking your medications and getting exercise



If a brain aneurysm leaks or ruptures, blood flows into the brain, damaging brain cells and increasing pressure inside the skull. This can cause permanent brain damage, a stroke, or other complications, including:

  • Vasospasm, a narrowing of the blood vessels, which reduces oxygen to the brain and can lead to stroke
  • “Water on the brain” (hydrocephalus), in which spinal fluid builds in the brain and places pressure on brain tissue
  • Changes to the level of sodium in the blood, which can cause brain cells to swell
  • Seizures
  • Coma
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Trust NewYork-Presbyterian for Brain Aneurysm Care

A brain aneurysm can be a life-threatening condition and requires expert care from a team of professionals. NewYork-Presbyterian is the busiest center in the tri-state area for the repair of brain aneurysms and the care of all neurologic disorders. The more experience a team has, the better the chance of a successful recovery. Contact us to make an appointment so we can create a personalized plan of care that meets your needs.