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Cerebral Aneurysm

An cerebral aneurysm is an abnormal widening or ballooning of a portion of an artery due to weakness in the wall of a blood vessel in the brain. Other common locations for aneurysms include the major artery from the heart (aorta), in the leg behind the knee (popliteal artery aneurysm), intestine (mesenteric artery aneurysm) and an artery in the spleen (splenic artery aneurysm).

An aneurysm may be congenital (present from birth) or it may develop later in life, such as after a blood vessel is injured. There are many different types of aneurysms. Berry aneurysms can vary in size from a few millimeters to more than a centimeter. Giant berry aneurysms, which are more common in adults, can grow to well over 2 centimeters.

Other types of cerebral aneurysm involve widening of an entire blood vessel, or they may appear as a ballooning out of part of a blood vessel. Atherosclerosis, trauma and infection, which can injure the blood vessel wall, can cause a cerebral aneurysm in any blood vessel that supplies the brain.

About 5 percent of the population has some type of aneurysm in the brain, but only a small number of these aneurysms cause symptoms or rupture. Risk factors include a family history of cerebral aneurysm and certain medical problems, such as polycystic kidney disease, coarctation of the aorta and high blood pressure.

Common Symptoms

Asymptomatic aneurysms – those without symptoms – may be discovered incidentally when an MRI or CT scan of the brain is performed for another reason.

Cerebral aneurysms may begin to leak a small amount of blood, causing a severe headache many people describe as “the worst headache of my life.” Known as sentinel headaches, the pain could be a warning sign of a rupture that may occur days or weeks afterwards. Symptoms may also occur if the aneurysm puts pressure on adjacent structures in the brain or ruptures (breaks open), causing bleeding into the brain.

Symptoms depend on the location of the aneurysm, whether it ruptures and the part of the brain affected. They may include:

  • Double vision
  • Loss of vision
  • Headaches
  • Eye pain
  • Neck pain
  • Stiff neck in rare cases

Symptoms of a ruptured aneurysm include:

  • A sudden, severe headache
  • Confusion, lethargy, sleepiness or stupor
  • Eyelid drooping
  • Headaches with nausea or vomiting
  • Muscle weakness or difficulty moving a part of the body
  • Numbness or decreased sensation in a part of the body
  • Seizures
  • Speech impairment
  • Vision changes such as double vision or loss of vision

A ruptured aneurysm is a medical emergency. Seek immediate medical help.


Your neurologist will perform an eye exam to look for evidence of increased pressure in the brain (elevated intracranial pressure), including swelling of the optic nerve or bleeding into the retina of the eye. A neurological exam may show abnormal eye movement, speech, strength or sensation.

We used the following tests to diagnose cerebral aneurysm and determine the cause of bleeding in the brain:

  • Cerebral angiograpy or spiral CT angiography of the head to reveal the location and size of the aneurysm
  • Lumbar puncture to examine the cerebrospinal fluid
  • CT scan of the head
  • Electroencephalogram (EEG)
  • MRI of the head


Your neurologist may refer you to a neurosurgeon for treatment to prevent a future, fatal rupture, even if your aneurysm shows no symptoms.

Not all aneurysms require immediate treatment. Those that are very small – less than 3 millimeters – are less likely to rupture.

An operation to "clip" the aneurysm is performed by doing a craniotomy (opening the skull surgically), and isolating the aneurysm from the bloodstream using one or more clips, which allows it to deflate. Surgical repair of cerebral aneurysms is not possible if they are located in unreachable parts of the brain. Angiography is used to visualize closure of the aneurysm and preserve normal flow of blood in the brain.

A less-invasive technique called endovascular therapy, uses micro catheters to deliver coils to the enlarged blood vessel; the coil closes up the aneurysm from inside the blood vessel. A procedure called balloon-assisted coiling uses a tiny balloon catheter to help hold the coil in place. A procedure called combination stent and coiling uses a small flexible cylindrical mesh tube that provides a scaffold for the coiling. Aneurysms may be treated with endovascular techniques when the risk of surgery is too high.

In general, patients with a ruptured cerebral aneurysm should be treated as soon as possible. Surgical risks and outcomes depend on whether or not the aneurysm has ruptured, the size and location of the aneurysm and the patient’s age and overall health.

Sources: National Institutes of Health and American Association of Neurological Surgeons

For More Information

The Brain Aneurysm Foundation
American Stroke Association

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