Aneurysm refers to abnormal widening of a blood vessel

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Man with glowing brain. Getty Images/Blend Images - John Lund/Brand X Pictures

Medical Specialties:

Family practice, Internal medicine, Neurology, Emergency medicine

Clinical Definition:

An aneurysm is an abnormal dilation, ballooning or bulging of the wall of an artery. It develops at a site of weakness. While aneurysms are more common in adults than children, they can occur at any age. Small aneurysms generally are not accompanied by symptoms, but those with a larger aneurysm may report vision problems or a loss of feeling in the face.

In Our Own Words:

Aneurysms, described most often as a ballooning or bulging of an artery wall, occurs at a point of weakness in the blood vessel wall. Aneurysms can occur anywhere, but two common sites are in the brain and the aorta. The exact cause is not known, but experts believe family history, a history of traumatic injury, smoking and hypertension (high blood pressure) may contribute to the risk. Aneurysms are more common in men than women, and family history and genetics can also play an important role.

More Information About Aneurysms

The worst thing that can happen with an aneurysm is that it bursts or ruptures. When an aneurysm ruptures, hemorrhagic shock and death can occur unless emergency surgery is performed.

Here is some more information about aortic and cerebral (brain) aneurysms.

Abdominal aortic aneurysms. These aneurysms occur in the abdominal aorta which is the largest blood vessel in the abdomen.

These aneurysms have a strong genetic component and run in families. When these aneurysms are greater than 5 cm in diameter, they need to be repaired. Clinical symptoms of these aneurysms include syncope or temporary loss of consciousness (preceded by a drop in blood pressure), flank pain, abdominal pain, back pain and bleeding.

Additionally, these aneurysms can throw out clots or emboli that choke off blood circulation to the arms and legs resulting in symptoms affecting the limbs. These aneurysms can be difficult to detect on physical exam--especially in obese individuals. Instead, these aneurysms are best detected using an abdominal CT scan, or in unstable patients, a rapid ultrasound is performed. Large and symptomatic abdominal aortic aneurysms require emergency surgery.

Cerebral aneurysms. Cerebral aneurysms typically occur at the level of the circle of Willis, which is a collection of arteries that supplies blood to the brain. Aneurysms affecting the blood vessels in the circle of Willis are called berry aneurysms. About 5 percent of all people have some sort of cerebral aneurysm; however, only a minority of these aneurysms actually rupture or burst. Much like aortic aneurysms, genetics predispose a person to the development of a berry aneurysm. Rupture of a berry aneurysm can result in a variety of symptoms including severe headache ("worst headache ever"), confusion, muscle weakness and trouble speaking.

In addition to clinical presentation, brain aneurysms are diagnosed using CT or MRI. If left untreated, a ruptured brain aneurysm is deadly. Treatment of brain aneurysms is surgical and involves either clipping or endovascular repair using coils. Endovascular repair is less invasive and more often performed than clipping. 


Cleveland Clinic. "Brain Aneurysm." Diseases and Conditions 2013. Accessed July 2013.

American Academy of Neurology. "Cerebral Aneurysms" 2013. Accessed July 2013.

American Academy of Neurology. "Cerebral Aneurysms” 2013. Accessed July 2013.

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