(HealthDay News) - An aneurysm occurs when a weakened portion of a blood vessel balloons or widens abnormally. There may be a throbbing or swelling sensation at the site, or no obvious symptoms.

The expanded portion of the vessel could be at risk of bursting, making immediate evaluation and treatment essential.

Here is additional information about aneurysms, courtesy of the U.S. National Library of Medicine:

• Aneurysms most frequently occur in or near the heart, brain, legs and intestines.
• It's unclear exactly what causes most aneurysms, but cholesterol buildup in the arteries is thought to play a role.
• High blood pressure also may contribute to aneurysms.
• If the blood vessel ruptures, low blood pressure, high heart rate and lightheadedness may result. The likelihood of death after a rupture is high.