What is a brain aneurysm?

An aneurysm is an abnormal, weak spot on a blood vessel that causes an outward bulging or ballooning of the arterial wall.  These weak spots can involve all walls of the blood vessel (fusiform aneurysm), form a sac from one wall (saccular) or separate the vessel walls (dissecting).  An aneurysm can affect any vessel in the body but only those in the head can cause a serious medical condition, a hemorrhagic stroke when they rupture, which can lead to brain damage and death.

It is estimated that up to one in 50 people in the United States will develop a brain aneurysm during their lifetime.

Brain aneurysms are often discovered when they rupture, causing bleeding into the brain or the space closely surrounding the brain called the subarachnoid space, causing a subarachnoid hemorrhage. Subarachnoid hemorrhage from a ruptured brain aneurysm can lead to a hemorrhagic stroke, brain damage and death.

The main goals of treatment once an aneurysm has ruptured are to stop the bleeding and potential permanent damage to the brain and to reduce the risk of recurrence. Unruptured brain aneurysms are sometimes treated to prevent rupture. Learn more about treatment options for a brain aneurysm.

Incidence Rates of Brain Aneurysms

  • Brain aneurysms are an uncommon disorder of the blood vessels that are usually acquired with age and affect approximately 6% of the United States population.
  • The annual incidence of aneurysmal subarachnoid hemorrhage in the U.S. exceeds 30,000 people. Ten to 15 percent of these patients will die before reaching the hospital and over 50 percent will die within the first thirty days after rupture. Of those who survive, about half suffer some permanent neurological deficit
  • The most significant risk factors are cigarette smoking and having a close relative who had an aneurysm.
  • The average age at presentation is usually 40 to 60 years old.
  • Aneurysms are found more commonly in females than in males (3:2), and 20% of patients have multiple (two or more) aneurysms.