A cerebral aneurysm is a weakened area in the wall of an artery in the brain that bulges or balloons out. The expanded portion of the vessel (the aneurysm) may push against surrounding nerves, causing symptoms. There is the risk that the aneurysm may rupture, causing bleeding into and around the brain (hemorrhage). This is a very serious medical condition that requires immediate treatment.

The majority of cerebral aneurysms do not cause symptoms until they become large or rupture. Symptoms may include pain around the eye area, numbness or weakness particularly on one side of the face and vision changes. If an aneurysm bursts, patients may experience a sudden, extremely severe headache, nausea and changes in mental status.

Most cerebral aneurysms are the result of a congenital abnormality, meaning the defect is present at birth. They are also more common in individuals with certain genetic diseases, and circulatory disorders. Some aneurysms develop as the result of head trauma, infection or drug abuse. There are no known ways to prevent the formation of an aneurysm.

It is estimated that between 10 and 15 million Americans have cerebral aneurysms. Of these, about 30,000 people experience an aneurysm rupture every year. Thus, most aneurysms do not rupture. They may remain small and stable and may not cause clear symptoms. Because of this, most aneurysms are not detected until they grow and rupture, or unless they are noticed as part of a screening for another condition. 

Several tests may be used to diagnose a cerebral aneurysm, however, they are often administered after a rupture. Angiography, CAT scan or MRI may be used to confirm the aneurysm, assess the extent of damage from the hemorrhage and help plan treatment.

The decision to treat an unruptured aneurysm with no symptoms is somewhat controversial. Physicians must weigh the patient’s overall health and risk of treatment against the chances of rupture. Factors taken into consideration include the age of the patient, the size and location of the aneurysm, the risk of rupture and the patient’s medical history. This decision is made on an individual basis and people are urged to get a second opinion if they are concerned with their initial evaluation and treatment plan.

If treatment is chosen, physicians may recommend surgery that involves clipping or clamping off the affected artery. Surgeons also may choose a procedure that places a coil into the aneurysm. The type of surgery to repair the aneurysm is based on a number of factors.

The prognosis varies greatly among individuals who develop a ruptured aneurysm. The major factors that affect a patient’s outlook include the location of the aneurysm, the extent of damage from the hemorrhage, the time between the rupture and medical attention and other health conditions.