A cerebral aneurysm (also called an intracranial aneurysm or brain aneurysm) is a bulging, weakened area in the wall of an artery in the brain, resulting in an abnormal widening, ballooning, or bleb. Because there is a weakened spot in the aneurysm wall, there is a risk for rupture (bursting) of the aneurysm.
A cerebral aneurysm more frequently occurs in an artery located in the front part of the brain that supplies oxygen-rich blood to the brain tissue. Arteries anywhere in the brain can develop aneurysms. A normal artery wall is made up of three layers. The aneurysm wall is thin and weak because of an abnormal loss or absence of the muscular layer of the artery wall, leaving only two layers.
The most common type of cerebral aneurysm is called a saccular, or berry, aneurysm, occurring in 90 percent of cerebral aneurysms. This type of aneurysm looks like a "berry" with a narrow stem. More than one aneurysm may be present.
Two other types of cerebral aneurysms are fusiform and dissecting aneurysms. A fusiform aneurysm bulges out on all sides (circumferentially), forming a dilated artery. Fusiform aneurysms are often associated with atherosclerosis.
A dissecting aneurysm results from a tear along the length of the artery in the inner layer of the artery wall, causing blood to leak in between the layers of the wall. This may cause a ballooning out on one side of the artery wall, or it may block off or obstruct blood flow through the artery. Dissecting aneurysms usually occur from traumatic injury, but they can also happen spontaneously. The shape and location of the aneurysm may determine which treatment is recommended.
Most cerebral aneurysms (90 percent) present without any symptoms and are small in size (less than 10 millimeters, or less than four-tenths of an inch, in diameter). Smaller aneurysms may have a lower risk of rupture.
Although a cerebral aneurysm may be present without symptoms, the most common initial symptom of a cerebral saccular aneurysm is a sudden headache from a subarachnoid hemorrhage (SAH). SAH is bleeding into the subarachnoid space (the space between the brain and the membranes that cover the brain) and not into the brain tissue. Minor subarachnoid hemorrhage most frequently occurs following head trauma. Major subarachnoid hemorrhage is most commonly from a ruptured cerebral saccular aneurysm (80 percent). A sudden headache associated with SAH is a medical emergency.
Increased risk for aneurysm rupture is associated with aneurysms that are over 10 millimeters (less than four-tenths of an inch) in diameter, a location (circulation in the back portion of the brain), and/or previous rupture of another aneurysm. A significant risk of death is associated with the rupture of a cerebral aneurysm.
Currently, the cause of cerebral aneurysms is not clearly understood. Brain aneurysms are associated with several factors, including smoking, hypertension, and family history (genetic). The ultimate cause of a brain aneurysm is an abnormal degenerative (breaking down) change (weakening) in the wall of an artery, and the effects of pressure from the pulsations of blood being pumped forward through the arteries in the brain. Certain locations of an aneurysm may create greater pressure on the aneurysm, such as at a bifurcation (where the artery divides into smaller branches).
Inherited risk factors associated with aneurysm formation may include, but are not limited to, the following:
Acquired risk factors associated with aneurysm formation may include, but are not limited to, the following:
A risk factor is anything that may increase a person's chance of developing a disease. It may be an activity, such as smoking, diet, family history, or many other things. Different diseases have different risk factors.
Although these risk factors increase a person's risk, they do not necessarily cause the disease. Some people with one or more risk factors never develop the disease, while others develop disease and have no known risk factors. Knowing your risk factors to any disease can help to guide you into the appropriate actions, including changing behaviors and being clinically monitored for the disease.
The presence of a cerebral aneurysm may not be known until the time of rupture. However, occasionally there may be symptoms that occur prior to an actual rupture due to a small amount of blood that may leak, called "sentinel hemorrhage" into the brain. Some aneurysms are symptomatic because they press on adjacent structures, such as nerves to the eye. They can cause visual loss or diminished eye movements, even if the aneurysm has not ruptured.
The symptoms of an unruptured cerebral aneurysm include, but are not limited to, the following:
The first evidence of a cerebral aneurysm is most frequently a subarachnoid hemorrhage (SAH), due to rupture of the aneurysm. Symptoms that may occur at the time of SAH include, but are not limited to, the following:
The symptoms of a cerebral aneurysm may resemble other problems or medical conditions. Always consult your doctor for a diagnosis.
A cerebral aneurysm is often discovered after it has ruptured or by chance during diagnostic examinations such as computed tomography (CT scan), magnetic resonance imaging (MRI), or angiography that are being done for other reasons.
In addition to a complete medical history and physical examination, diagnostic procedures for a cerebral aneurysm may include:
Specific treatment for a cerebral aneurysm will be determined by your doctor based on:
Depending on your situation, the doctor will make recommendations for the intervention that is appropriate. Whichever intervention is chosen, the main goal is to decrease the risk of subarachnoid hemorrhage, either initially or from a repeated episode of bleeding.
Many factors are considered when making treatment decisions for a cerebral aneurysm. The size and location of the aneurysm, the presence or absence of symptoms, the patient's age and medical condition, and the presence or absence of other risk factors for aneurysm rupture are considered. In some cases, the aneurysm may not be treated and the patient will be closely followed by a doctor. In other cases, surgical treatment may be indicated.
There are two primary surgical treatments for a cerebral aneurysm:
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