What is an Aneurysm?

Cerebral aneurysm

A cerebral or intracranial aneurysm is an abnormal focal dilation of an artery in the brain that results from a weakening of the inner muscular layer (the intima) of a blood vessel wall. The vessel develops a "blister-like" dilation that can become thin and rupture without warning. The resultant bleeding into the space around the brain is called a subarachnoid hemorrhage (SAH). This kind of hemorrhage can lead to a stroke, coma, and/or death.

Aneurysms are usually found at the base of the brain just inside the skull, in an area called the subarachnoid space. In fact, 90 percent of SAHs are attributed to ruptured cerebral aneurysms and the two terms are often used synonymously.

Aneurysms range in size, from small – about 1/8 inch – to nearly one inch. Aneurysms larger than one inch are called giant aneurysms, pose a particularly high risk, and are difficult to treat. The exact mechanisms by which cerebral aneurysms develop, grow and rupture are unknown.

Carotid-ophthalmic artery aneurysm

However, a number of factors are believed to contribute to the formation of cerebral aneurysms, including:

  • hypertension (high blood pressure);

  • cigarette smoking;

  • congenital (genetic) predisposition;

  • injury or trauma to blood vessels;

  • complication from some types of blood infections.

Patients with intracranial aneurysms can present with SAH from aneurysmal rupture or with un-ruptured aneurysms, which may have been discovered incidentally or resulted in neurological symptoms. An aneurysm ruptures when a hole develops in the sac of the aneurysm. The hole can be small, in which case only a small amount of blood leaks, or large, leading to a major hemorrhage. An un-ruptured aneurysm is the one whose sac has not previously leaked. Every year approximately 30,000 patients in the U.S. suffer from a ruptured cerebral aneurysm, and up to 6 percent of the population may have an un-ruptured cerebral aneurysm.

Treatment Options

Ruptured aneurysms are typically treated in one of two ways:

  • Endovascular coiling

  • Microsurgical clipping

Unruptured aneurysms may be treated in the same way via endovascular coiling or microsurgical clipping, but the decision as to whether they should be treated is based on a number of different factors.

These factors include:

  • Age

  • Medical Comorbidities

  • Size of aneurysm

  • Location of aneurysm

  • Etc

Cerebral Aneurysm Resources

The Brain Aneurysm Foundation
American Stroke Association

Reproduced by permission of the copyright owner. American Association of Neurological Surgeons, 5550 Meadowbrook Dr., Rolling Meadows, IL  60008. Further reproduction prohibited without permission, 2016.

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