Brain Aneurysm
(Cerebral Aneurysm)
Medical Author: Benjamin C. Wedro, MD, FAAEM
Medical Editor: Melissa Conrad Stöppler, MD
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Aneurysms - Frequently Asked Questions
Medical Author: Melissa Conrad Stöppler, MD
Medical Editor: Dennis Lee, MD

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.
Another type of aneurysm is a
brain aneurysm. Brain aneurysms are widened areas of arteries or veins
within the brain itself. These may be caused by head injury, an inherited (congenital) malformation of the vessels, high blood
pressure, or atherosclerosis. A special type of brain aneurysm is known as a
berry aneurysm. Berry aneurysms are small, berry-shaped outpouchings of the main
arteries that supply the brain and are particularly dangerous since they are
susceptible to rupture, leading to often fatal bleeding within the brain. Brain
aneurysms can occur at any age but are more common in adults than in children.
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What is a brain aneurysm and what causes a brain aneurysm?
The brain gets its blood supply from arteries known as the Circle of Willis.
It is located at the base of the brain and is a loop of arteries that join in a
circle then send branches out to all parts of the brain. These arteries
deliver nutrition (glucose and oxygen) to the brain cells.
The junctions where these arteries come together can form 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 tissues. While the prevailing thought has been
that aneurysms are congenital (meaning that people are born with them), it is now
thought that they are due to microscopic damage to the artery walls caused by
abnormal flow at the junction points where the arteries come together.
There are other rare causes of aneurysms. Mycotic aneurysms are cause 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 (aneurysms within arteries in the brain) are a common
occurrence. At autopsy,
incidental asymptomatic aneurysms are found in more than 1% of people. Most
aneurysms remain small and never become an issue or are diagnosed. Some,
however, may gradually get larger and exert pressure on surrounding brain tissue
and nerves and may be diagnosed because of facial symptoms such as:
- 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. Bleeding leaks into one of the membranes
that covers the brain and spinal canal and is known as a subarachnoid hemorrhage
(sub= beneath + arachnoid=one of the brain coverings + hemorrhage=bleeding).
Next: What are the symptoms of brain aneurysm? »
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Last Editorial Review: 1/9/2008