Cerebral Aneurysm

A cerebral aneurysm is a weak spot on the wall of an artery in the brain that can balloon out and burst. Most aneurysms are silent until they begin to bleed, causing a stroke, or grow to a size that pushes on a nerve or the surrounding brain.


There usually are few symptoms of a brain aneurysm. Sometimes, brain aneurysms press on a nerve or leak small amounts of blood before a major rupture, thus producing warning signs. If you have the following symptoms (minutes or weeks before the rupture), you should see a doctor quickly so that steps can be taken to prevent a massive hemorrhage:

  • Severe headache
  • Pain behind one eye
  • Double vision, droopy eyelid or other vision problems

An actual rupture can produce the following symptoms:

  • A sudden, severe headache
  • A brief loss of consciousness that often follows the onset of the headache. Some people remain in a coma, but most often patients wake up feeling confused and sleepy. Within a few minutes or few hours, the patient may again begin to feel confused and sleepy
  • Vomiting
  • Dizziness
  • Frequent fluctuations in the heartbeat and breathing rate often occur
  • Seizures
  • Paralysis on one side of the body or neurologic problems (usually occurring in about 25 percent of the people who have subarachnoid hemorrhages)

Causes and Risk Factors

Aneurysms most likely are conditions a person has at birth. The weak spot may not start ballooning out until later in adulthood. As the aneurysm becomes larger and the balloon wall becomes thinner, the risk of the aneurysm bursting grows. Research tends to show that people who smoke are more likely to have aneurysms that rupture. People who have uncontrolled high blood pressure also may have a greater risk of a ruptured aneurysm.

Certain diseases that run in families appear to be linked to brain aneurysms.  People with a family history of polycystic kidney disease and brain aneurysms should be screened.


A magnetic resonance angiogram (MRA) is used to screen for unruptured brain aneurysms. At this point, there is some small evidence to suggest that aneurysms run in families. Ongoing genetic studies are being done to investigate this possibility.

Because brain aneurysms are silent until they cause bleeding into the brain, a timely diagnosis can be difficult. The diagnosis of a subarachnoid hemorrhage can usually be made with a computed tomography (CT) scan. If the CT scan is not conclusive, a lumbar puncture (spinal tap) can be done to confirm or rule out the diagnosis.

Approximately 40 percent of those who have a subarachnoid hemorrhage die during the hemorrhage because of extensive brain damage. Without proper treatment for the brain aneurysm, 20 to 30 percent will have a second bleed within the first month and those who survive three months have approximately a three percent chance every year of having another episode of bleeding. Recurrent bleeding has a 70 percent mortality rate. Because of the ominous prognosis with delayed definitive therapy, referral to a center of excellence with experience in treating subarachnoid hemorrhage is imperative.


There are two basic approaches to treating an aneurysm:

  • The traditional approach, which involves making a window in the skull to repair the aneurysm by surgically clipping it, or
  • Coil embolization, which is threading a small tube into the aneurysm through an artery in the brain and packing the aneurysm with platinum coils.

Traditional Surgery

With this approach, surgery is done to clip the aneurysm. First a window is made in the skull. This is called a craniotomy. This allows the surgeon to get inside the skull to find the aneurysm. Aneurysms usually occur just under the brain or between the lobes of the brain.

It isn't usually necessary to cut into the brain to remove the aneurysm.

Once the aneurysm is exposed and dissected, a small, hinged aneurysm clip is placed on the neck of the aneurysm to seal off the weakened part of the artery.

For small aneurysms, this surgery can be done safely with a relatively low risk (about five percent) of complications. The risks are greater - 30 percent or more - for aneurysms that are complex, an inch or larger or located in the back part of the brain.

Sometimes more complex surgery, such as cerebral artery bypass or deliberate cardiac standstill are needed for more complex aneurysms.

Coil Embolization

With coil embolization, small platinum coils are placed into the bulge of the aneurysm to seal it off while preserving the normal blood flow of the artery.

This procedure does not require a craniotomy or any incision on the head. The procedure is done in a radiology suite where angiograms are done. It is done under general anesthesia.

During the procedure, a small tube is placed through an artery in the groin. The tube is advanced up to the arteries in the neck. Another smaller tube is threaded through the first one. Small platinum coils are delivered to the aneurysm through the second tube. They block off the ballooned part of the artery. The normal opening of the artery is left clear.

Although this treatment may successful cure the aneurysm, there are, as in surgery, risks to the procedure including complications such as stroke or aneurysm rupture. The overall risk of any complication occurring with this procedure for small aneurysms with a small neck is typically less than five percent. However, the aneurysm's size, location and shape and complexity all affect the risks. It's important to discuss these factors with your surgeon.

Some aneurysms that have a wide neck may need a stent to help keep the coils in the aneurysm.

If an aneurysm has ruptured, there are other risks even after treatment. The bleeding in the brain may set off a chain reaction that can cause complications.  Report anything unusual to your doctor so a close watch can be kept on your condition to deal with these possible complications as soon as they arise. They include: