Aneurysms in the brain occur when there is a weakened area in the wall of a blood vessel. An aneurysm may be present from birth (congenital). Or, it may develop later in life, such as after a blood vessel is injured.
There are many types of brain aneurysms. The most common type is called a berry aneurysm. This type can vary in size from a few millimeters to over a centimeter. Giant berry aneurysms can be bigger than 2 centimeters. These are more common in adults. Berry aneurysms are passed down through families more often than other types of aneurysms.
Other types of cerebral aneurysms involve widening of an entire blood vessel. Or, they may appear as a ballooning out of part of a blood vessel. Such aneurysms can occur in any blood vessel that supplies the brain. Atherosclerosis, trauma, and infection can all injure the blood vessel wall and cause cerebral aneurysms.
About 5% of people have a brain aneurysm, but only a small number of these aneurysms cause symptoms or rupture.
A person may have an aneurysm without having any symptoms. This kind of aneurysm may be found when an MRI or CT scan of the brain is done for another reason.
A cerebral aneurysm may begin to leak a small amount of blood. This may cause a severe headache that a patient may describe as "the worst headache of my life." It may be called a thunderclap or sentinel headache. This means the headache could be a warning sign of a future rupture that may occur days to weeks after the headache first started.
Symptoms may also occur if the aneurysm pushes on nearby structures in the brain or breaks open (ruptures) and causes bleeding into the brain.
Symptoms depend on the location of the aneurysm, whether it breaks open, and what part of the brain it is pushing on. Symptoms may include:
Loss of vision
Ringing in the ears
A sudden, severe headache is one symptom of an aneurysm that has ruptured. Other symptoms of an aneurysm rupture may include:
NOTE: A ruptured aneurysm is a medical emergency. Call your local emergency number, such as 911.
Exams and Tests
An eye exam may show signs of increased pressure in the brain, including swelling of the optic nerve or bleeding into the retina of the eye. A brain and nervous system exam may show abnormal eye movement, speech, strength, or sensation.
The following tests may be used to diagnose a cerebral aneurysm and determine the cause of bleeding in the brain:
Cerebral angiography or spiral CT scan angiography of the head to show the location and size of the aneurysm
Endovascular repair is most often done. It usually involves a coil or coiling. This is a less invasive way to treat some aneurysms.
If an aneurysm in the brain ruptures, it is an emergency that needs medical treatment and often requires surgery. Endovascular repair is often used when this happens.
Even if there are no symptoms, your doctor may order treatment to prevent a future, and possibly fatal rupture.
Not all aneurysms need to be treated right away. Those that are very small (less than 3 mm) are less likely to break open.
Your doctor will help you decide whether or not it is safer to have surgery to block off the aneurysm before it can break open (rupture). Sometimes people are too ill to have surgery, or it may be too dangerous to treat the aneurysm because of its location.
Treatment of a ruptured aneurysm may involve:
Being admitted to the hospital's intensive care unit (ICU)
Complete bedrest and activity restrictions
Drainage of blood from the brain area (cerebral ventricular drainage)
Drugs to prevent seizures
Drugs to control headaches and blood pressure
Drugs through a vein (IV) to prevent infection
Once the aneurysm is repaired, the person may need to prevent a stroke from a blood vessel spasm.
How well you do depends on many things. People who are in a deep coma after an aneurysm rupture do not do as well as those with less severe symptoms.
Ruptured cerebral aneurysms are often deadly. Of those who survive, about 1 in 4 will have some sort of permanent disability.
Go to the emergency room or call the local emergency number (such as 911) if you have a sudden or severe headache, especially if you also have nausea, vomiting, seizures, or any other nervous system symptom.
Also call if you have a headache that is unusual for you, especially if it is severe or your worst headache ever.
There is no known way to prevent a berry aneurysm from forming. Treating high blood pressure may reduce the chance that an existing aneurysm will rupture. Controlling risk factors for atherosclerosis may reduce the likelihood of some types of aneurysms.
People who are known to have an aneurysm may need regular doctor visits to make sure the aneurysm is not changing size or shape.
If unruptured aneurysms are discovered in time, they can be treated before causing problems.
The decision to repair an unruptured cerebral aneurysm is based on the size and location of the aneurysm, and the patient's age and general health.
Bederson JB, Connolly ES Jr, Batjer HH, et al: American Heart Association Guidelines for the management of aneurysmal subarachnoid hemorrhage: a statement for healthcare professionals from a special writing group of the Stroke Council, American Heart Association. Stroke. 2009;40:994-1025.
Bowles E. Cerebral aneurysm and aneurysmal subarachnoid hemorrhage. Nurs Stand. 2014;28:52-59.
Mack W, Dusick JR, Martin N, Gonzalez N. Principles of endovascular therapy. In: Daroff RB, Fenichel GM, Jankovic J, Mazziotta JC, eds. Bradley's Neurology in Clinical Practice. 6th ed. Philadelphia, PA: Elsevier Saunders; 2012:chap 47.
Meyers PM, Schumacher HC, Higashida RT, et al: American Heart Association. Indications for the performance of intracranial endovascular neurointerventional procedures: a scientific statement from the American Heart Association Council on Cardiovascular Radiology and Intervention. Stroke Council, council on Cardiovascular Surgery and Anesthesia, Interdisciplinary Council on Peripheral Vascular Disease, and Interdisciplinary Council on Quality of Care and Outcomes Research. Circulation. 2009;119:2235-2249.
Joseph V. Campellone, MD, Department of Neurology, Cooper University Hospital, Camden, NJ. Review provided by VeriMed Healthcare Network. Also reviewed by David Zieve, MD, MHA, Isla Ogilvie, PhD, and the A.D.A.M. Editorial team.