Brain Aneurysm

A brain aneurysm is an abnormal bulge or “ballooning” in the wall of an artery in the brain.

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They are sometimes called berry aneurysms because they are often the size of a small berry. Most brain aneurysms produce no symptoms until they become large, begin to leak blood, or burst.

If a brain aneurysm presses on nerves in your brain, it can cause signs and symptoms. These can include

  • A droopy eyelid
  • Double vision or other changes in vision
  • Pain above or behind the eye
  • A dilated pupil
  • Numbness or weakness on one side of the face or body

Treatment depends on the size and location of the aneurysm, whether it is infected, and whether it has burst. If a brain aneurysm bursts, symptoms can include a sudden, severe headache, nausea and vomiting, stiff neck, loss of consciousness, and signs of a stroke. Any of these symptoms requires immediate medical attention.



There are no known ways to prevent a cerebral aneurysm from forming. People with a diagnosed brain aneurysm should carefully control high blood pressure, stop smoking, and avoid cocaine use or other stimulant drugs. They should also consult with a doctor about the benefits and risks of taking aspirin or other drugs that thin the blood. Women should check with their doctors about the use of oral contraceptives.


Risk Factors

Brain aneurysms can occur in anyone, at any age. They are more common in adults than in children and slightly more common in women than in men. People with certain inherited disorders are also at higher risk.

All cerebral aneurysms have the potential to rupture and cause bleeding within the brain. The incidence of reported ruptured aneurysm is about 10 in every 100,000 persons per year (about 30,000 individuals per year in the U.S.), most commonly in people between ages 30 and 60 years.


  • Hypertension (high blood pressure)
  • Alcohol abuse
  • Drug abuse (particularly cocaine)
  • Smoking
  • The condition and size of the aneurysm



Cerebral aneurysms can be congenital, resulting from an inborn abnormality in an artery wall. Cerebral aneurysms are also more common in people with certain genetic diseases, such as connective tissue disorders and polycystic kidney disease, and certain circulatory disorders, such as arteriovenous malformations (snarled tangles of arteries and veins in the brain that disrupt blood flow).


  • Trauma or injury to the head
  • Hypertension (high blood pressure)
  • Infection
  • Tumors
  • Atherosclerosis and other diseases of the vascular system
  • Smoking
  • Drug abuse.

Some investigators have also speculated that oral contraceptives may increase the risk of developing aneurysms.



Most cerebral aneurysms do not show symptoms until they either become very large or burst. Small, unchanging aneurysms generally will not produce symptoms, whereas a larger aneurysm that is steadily growing may press on tissues and nerves.


  • Pain above and behind the eye
  • Numbness, weakness, or paralysis on one side of the face
  • Dilated pupils
  • Vision changes.


  • A sudden and extremely severe headache
  • Double vision
  • Nausea
  • Vomiting
  • Stiff neck
  • Loss of consciousness.

Individuals usually describe the headache as “the worst headache of my life” and it is generally different in severity and intensity from other headaches people may experience. “Sentinel” or warning headaches may result from an aneurysm that leaks for days to weeks prior to rupture. Only a minority of individuals have a sentinel headache prior to aneurysm rupture.


  • Nausea and vomiting associated with a severe headache
  • A drooping eyelid
  • Sensitivity to light
  • Change in mental status or level of awareness.
  • Seizures.
  • Loss of consciousness and/or prolonged coma.

People experiencing this “worst headache,” especially when it is combined with any other symptoms, should seek immediate medical attention.



Most cerebral aneurysms go unnoticed until they rupture or are detected by brain imaging that may have been obtained for another condition. Several diagnostic methods are available to provide information about the aneurysm and the best form of treatment. The tests are usually obtained after a subarachnoid hemorrhage, to confirm the diagnosis of an aneurysm.



Not all cerebral aneurysms burst. Some people with very small aneurysms may be monitored to detect any growth or onset of symptoms and to ensure aggressive treatment of coexisting medical problems and risk factors. Each case is unique, and considerations for treating an unruptured aneurysm include the type, size, and location of the aneurysm; risk of rupture; the individual’s age, health, and personal and family medical history; and risk of treatment.


Microvascular clipping involves cutting off the flow of blood to the aneurysm. Clipping has been shown to be highly effective, depending on the location, shape, and size of the aneurysm. In general, aneurysms that are completely clipped surgically do not return.

A related procedure is an occlusion, in which the surgeon clamps off (occludes) the entire artery that leads to the aneurysm. This procedure is often performed when the aneurysm has damaged the artery.


Endovascular embolization is an alternative to surgery. This procedure fills the aneurysm, blocks it from circulation, and causes the blood to clot, which effectively destroys it. The procedure may need to be performed more than once during the person’s lifetime.

People who receive treatment for an aneurysm must remain in bed until the bleeding stops. Underlying conditions, such as high blood pressure, should be treated.


An unruptured aneurysm may go unnoticed throughout a person’s lifetime. A burst aneurysm, however, may be fatal or could lead to hemorrhagic stroke, vasospasm (the leading cause of disability or death following a burst aneurysm), hydrocephalus, coma, or short-term and/or permanent brain damage.

The prognosis for persons whose aneurysm has burst is largely dependent on the age and general health of the individual, other pre-existing neurological conditions, location of the aneurysm, extent of bleeding (and rebleeding), and time between rupture and medical attention.

It is estimated that about 40 percent of individuals whose aneurysm has ruptured do not survive the first 24 hours; up to another 25 percent die from complications within 6 months. Other individuals may recover with little or no neurological deficit. Early diagnosis and treatment are important.

Individuals who receive treatment for an unruptured aneurysm generally require less rehabilitative therapy and recover more quickly than persons whose aneurysm has burst. Recovery from treatment or rupture may take weeks to months.

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