What is an unruptured aneurysm?
An aneurysm is a balloon-like bulge or weakening of an arterial wall. As the bulge grows it becomes thinner and weaker. It can become so thin that the blood pressure within it can cause it to burst or leak. Most aneurysms develop from a weakness or abnormal artery wall. Aneurysms usually occur on larger blood vessels where an artery branches. Approximately 80% of aneurysms form in the front (anterior circulation) of the brain, while 20% form in the back (posterior circulation) of the brain. Types of aneurysms include (Fig. 2):
What are the symptoms?
Most aneurysms don't have symptoms (asymptomatic) until they rupture. Ruptured aneurysms release blood into the spaces around the brain called a subarachnoid hemorrhage (SAH). Unruptured aneurysms rarely show symptoms until they grow large or press on vital structures. Rupture usually occurs while a person is active rather than asleep. If you experience the symptoms of a SAH, call 911 immediately!
Symptoms of an unruptured aneurysm:
Symptoms of a ruptured aneurysm or subarachnoid hemorrhage (SAH):
What are the causes?
Studies have shown a strong link to family history (2). If an immediate family member has suffered an aneurysm, you are 4 times more likely to have one as well. The genetic link is not completely understood and studies are underway to determine if there is a pattern of inheritance. The most important inherited conditions associated with aneurysms include Ehlers-Danlos IV, Marfans syndrome, neurofibromatosis NF1, and polycystic kidney disease. For those with a strong family history, we recommend a screening test (CT or MR angiogram).
Who is affected?
Approximately 5% of the population may have or develop an aneurysm; of those, 20% have multiple aneurysms. Unruptured aneurysms are more common (2.7 million per year) than ruptured (20,000 per year) (1). However, 85% of aneurysms are not diagnosed until after they rupture. Aneurysms are usually diagnosed between ages 35 to 60 and are more common in women.
How is a diagnosis made?
Most people find out they have an unruptured aneurysm by chance (incidental) during a scan for some other medical problem. If you are experiencing symptoms and your primary care doctor suspects an aneurysm, you may be referred to a neurosurgeon. The doctor will learn as much about your symptoms, current and previous medical problems, current medications, family history, and perform a physical exam. Diagnostic tests are used to help determine the aneurysm's location, size, type, and involvement with other structures.
Should the aneurysm be treated?
Deciding how, or even if, to treat an unruptured aneurysm involves weighing the risks of rupture versus the risks of treatment. The risk of aneurysm rupture is about 1% but may be higher or lower depending on the size and location of the aneurysm; however, when a rupture occurs there is a 50% risk of death. Risk factors for rupture include smoking, high blood pressure, alcohol, genetic factors (family inherited), atherosclerosis (hardening of the arteries), oral contraceptives, and lifestyle (3). Other factors such as the size and location of the aneurysm, overall health of the patient, and medical history must also be considered. Generally, the larger the aneurysm, the higher risk of rupture. Also, aneurysms in the posterior circulation (basilar, vertebral and posterior communicating arteries) have a higher risk of rupture. The neurosurgeon will discuss with you all the options and recommend a treatment that is best for your individual case.
What treatments are available?
Artery occlusion and bypass
A bypass can also be created by detaching a donor artery from its normal position on one end, redirecting it to the inside of the skull, and connecting it above the blocked artery. This is called a STA-MCA (superficial temporal artery to middle cerebral artery) bypass.
Clinical trials are research studies in which new treatments—drugs, diagnostics, procedures, and other therapies—are tested in people to see if they are safe and effective. Research is always being conducted to improve the standard of medical care. Information about current clinical trials, including eligibility, protocol, and locations, are found on the Web. Studies can be sponsored by the National Institutes of Health (see clinicaltrials.gov) as well as private industry and pharmaceutical companies (see www.centerwatch.com).
Recovery & prevention
Unruptured aneurysm patients recover from surgery or endovascular treatment much faster than those who suffer a SAH. The possibility of having a second bleed is 35% within the first 14 days after the first bleed. This is why neurosurgeons prefer to do direct surgical or endovascular treatment as soon as the aneurysm is diagnosed, so that the risk of a rebleed is lessened.
Aneurysm patients may suffer short-term and/or long-term deficits as a result of a treatment or rupture. Some of these deficits may disappear over time with healing and therapy.
Sources & links
If you have more questions, please contact the Mayfield Clinic at 800-325-7787 or 513-221-1100. For information about the University of Cincinnati Neuroscience Institute’s Neurovascular Center, call 866-941-8264.
aneurysm: a bulge or weakening of an arterial wall.
coiling: a procedure to insert platinum coils into an aneurysm; performed during an angiogram.
craniotomy: surgical opening in the skull.
Ehlers-Danlos IV: a genetic disorder of the connective tissue in the intestines, arteries, uterus, and other hollow organs may be unusually weak, leading to organ or blood vessel rupture.
embolization: inserting material, coil or glue, into an aneurysm so blood can no longer flow through it.
inherited: to receive from a parent or ancestor by genetic transmission.
Marfans syndrome: a genetic disorder in which patients develop skeletal defects in long bones, chest abnormalities, curvature of the spine, and circulatory defects.
neurofibromatosis (NF1): a genetic disorder, also called von Recklinghausen disease, in which patients develop café-au-lait spots, freckling, and multiple soft tumors under the skin and throughout the nervous system.
polycystic kidney disease: a genetic disorder in which patients develop multiple cysts on the kidneys; associated with aneurysms of blood vessels in the brain.
subarachnoid hemorrhage (SAH): bleeding in the space between the brain and skull; may cause a stroke.
vasospasm: abnormal narrowing or tightening of arteries due to irritation by blood in the subarachnoid space.