What is a brain aneurysm?

A brain aneurysm (also called a cerebral aneurysm) is a blister-like bulge in a weak part of a blood vessel in your brain. It can go unnoticed for a long time. In fact, 1-6 percent of Americans has an aneurysm they don’t know about. If left untreated, however, the pressure of the blood causes that area of wall of the blood vessel to become even weaker, which allows the aneurysm to grow. Eventually the aneurysm may burst, which causes a stroke.

What do I need to know?

A few simple rules will help you avoid a brain aneurysm and/or help you receive essential and timely treatment.

  • Know the risk factors and create a lifestyle that helps you avoid an aneurysm in the first place
  • If you are at risk for brain aneurysm, talk with your doctor about getting screened for early detection
  • Know the signs and symptoms of both a brain aneurysm and a ruptured aneurysm and be certain your friends and family members do, too
  • If you experience any of the symptoms, call 911 so you can receive treatment right away

Where in the brain do aneurysms develop?

The internal carotid arteries are the two large arteries – located on either side of the head and neck – that supply blood to the brain.

The most common types of aneurysms are found in the arteries that connect the two internal carotid arteries:

  • 30% of aneurysms form in the anterior communicating artery (AComm)
  • 25% form in the posterior communicating artery (PComm)

The frequency of aneurysms in other locations:

  • 20% in the middle cerebral artery (MCA), which supply blood to the front of the brain 
  • 7.5% in the internal carotid arteries themselves, called ICA bifurcation
  • 7% in the tip of the basilar artery, which runs along the middle of the brain, where it divides into two smaller arteries
  • 4% in the pericallosal artery, which is a segment of another important pair of arteries called the anterior carotid arteries
  • 3% in the posterior inferior cerebellar artery (PICA), which supplies blood to the bottom portion of the brain

A small percentage of aneurysms form in other areas of the brain as well.