Brain Aneurysm
(Cerebral Aneurysm)

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Brain aneurysm facts

  • Blood to the brain is supplied by four major blood vessels that join together at the Circle of Willis at the base of the brain. Smaller branch arteries leave the circle to supply brain cells with oxygen and nutrients.
  • Artery junction points may become weak, causing ballooning of the blood vessel wall that can form a small sac or aneurysm.
  • Cerebral aneurysms are common, but most are asymptomatic and are found incidentally at autopsy.
  • Aneurysms can leak or rupture causing symptoms from severe headache to stroke-like symptoms, or death.
  • The health care practitioner needs to maintain a high incidence of suspicion to make the diagnosis, since many patients may have an initial small leak of blood causing symptoms before a catastrophic bleed occurs.
  • Diagnosis of a brain aneurysm may require CT scans, lumbar puncture, or angiography.
  • Treatment to repair the aneurysm may involve surgery to put a clip across the weak blood vessel wall. A coil may also be used to fill the aneurysm to prevent bleeding.

What is a brain aneurysm and what causes a brain aneurysm?

The Circle of Willis is the junction of the four many arteries, two carotid arteries and two vertebral arteries, that supply the brain with nutrition (oxygen and glucose). This loop of arteries is located at the base of the brain and sends out smaller branch arteries to all parts of the brain. The junctions where these arteries come together may develop weak spots. These weak spots can balloon out and fill with blood, creating the outpouchings of blood vessels known as aneurysms. These sac-like areas may leak or rupture, spilling blood into surrounding brain tissue.

Aneurysms have a variety of causes including high blood pressure and atherosclerosis, trauma, heredity, and abnormal blood flow at the junction where arteries come together.

There are other rare causes of aneurysms. Mycotic aneurysms are caused by infections of the artery wall. Tumors and trauma can also cause aneurysms to form. Drug abuse, especially cocaine, can cause the artery walls to inflame and weaken.

Brain aneurysms are a common occurrence. At autopsy, incidental aneurysms that have never caused any symptoms or issues are found in more than 1% of people. Most aneurysms remain small and are never diagnosed. Some, however, may gradually become larger and exert pressure on surrounding brain tissue and nerves and may be diagnosed because of stroke-like symptoms including:

  • headache,
  • numbness, or weakness of one side of the face,
  • a dilated pupil, or
  • change in vision.

The greater concern is a brain aneurysm that leaks or ruptures, and potentially causes stroke or death. Blood may leak into one of the membranes (meninges) that covers the brain and spinal canal and is known as a subarachnoid hemorrhage (sub= beneath + arachnoid=one of the brain coverings + hemorrhage=bleeding).

Picture of a brain aneurysm
Picture of a brain aneurysm
Medically Reviewed by a Doctor on 3/25/2014

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Brain Aneurysms Can Be Deadly

Aneurysms - Frequently Asked Questions

What are some common types of aneurysms?

The most common types of aneurysms involve the aorta, the large vessel that carries oxygen-containing blood away from the heart. In particular, aneurysms most commonly develop in the abdominal portion of the aorta and are designated abdominal aortic aneurysms. Abdominal aortic aneurysms are most common in men over the age of 60. Most aortic aneurysms are caused by atherosclerosis ("hardening of the arteries") since this condition can weaken the walls of the aorta and lead to thinning and widening of the affected areas.


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