Cerebral Aneurysm

A cerebral (or cranial) aneurysm is an area where a blood vessel in the brain weakens, resulting in a bulging or ballooning out of part of the vessel wall. Usually, aneurysms develop at the point where a blood vessel branches, because the 'fork' is structurally more vulnerable. The disorder may result from congenital defects or from other conditions such as high blood pressure, atherosclerosis (the build-up of fatty deposits in the arteries), or head trauma.

Every year, an estimated 30,000 people in the United States experience a ruptured cerebral aneurysm, and up to 6 percent of the population may be living with an unruptured aneurysm. Aneurysms occur in all age groups, but the incidence increases steadily for individuals age 25 and older, is most prevalent in people ages 50 to 60, and about three times more prevalent in women. The outcome for patients treated before a ruptured aneurysm is much better than for those treated after, so the need for adequate evaluation of patients suspected of having a cerebral aneurysm is very important.

Unruptured cerebral aneurysms can be detected by noninvasive measures, including magnetic resonance angiography (MRA) and a carotid angiogram. A rupture can be detected by a computerized tomography (CT or CAT scan) or lumbar puncture. If these tests suggest the presence of an aneurysm, formal cerebral angiography may be performed.

Complications

When cerebral aneurysms rupture, they usually cause bleeding in the brain, resulting in a subarachnoid hemorrhage. Blood can also leak into the cerebrospinal fluid (CSF) or areas surrounding the brain and cause an intracranial hematoma (a blood clot). Blood can irritate, damage, or destroy nearby brain cells. This may cause problems with bodily functions or mental skills. In more serious cases, the bleeding may cause brain damage, paralysis or coma. Ruptured brain aneurysms are fatal in about 50 percent of cases. Blood leaking around the brain may cause vasospasm, a narrowing of the blood vessels, which decreases the amount of blood supplied to the brain, and may result in a stroke. Vasospasm usually develops 5-8 days after the initial hemorrhage. To treat vasospasm, blood pressure is often elevated with medications. Another procedure requires the use of tiny balloon catheters that are inserted in a micro catheter through an artery, and then threaded into the affected blood vessels. Once in place, a balloon is inflated to widen the affected blood vessels and increase blood flow. Catheters can also be used to administer medication directly, to help increase the flow of blood.

Blood from a ruptured aneurysm can block CSF circulation, leading to hydrocephalus, a condition in which excess CSF builds up within the ventricles (fluid-containing cavities) of the brain. This may increase pressure within the head. Fluid may also build up in the brain after surgery to repair the aneurysm. To stop fluid from building up, a drain may be placed in the ventricles, to remove excess CSF and blood that has leaked.

Surgery and Treatment

An operation to "clip" the aneurysm is performed by doing a craniotomy (opening the skull surgically), and isolating the aneurysm from the bloodstream using one or more clips, which allows it to deflate. Surgical repair of cerebral aneurysms is not possible if they are located in unreachable parts of the brain. Angiography is used to visualize closure of the aneurysm and preserve normal flow of blood in the brain.

A less invasive technique which does not require an operation, called endovascular therapy, uses micro catheters to deliver coils to the site of the enlarged blood vessel that occludes (closes up) the aneurysm from inside the blood vessel. A procedure called balloon assisted coiling uses a tiny balloon catheter to help hold the coil in place. A procedure called combination stent and coiling utilizes a small flexible cylindrical mesh tube that provides a scaffold for the coiling. Aneurysms may be treated with endovascular techniques when the risk of surgery is too high.

While the best method of securing the aneurysm should be made on an individual basis, in general, patients with a ruptured cerebral aneurysm should be treated as soon as possible. Surgical risks and outcomes depend on whether or not the aneurysm has ruptured, the size and location of the aneurysm, and the patient’s age and overall health.

Cerebral Aneurysm Resources

The Brain Aneurysm Foundation

Brain Aneurysm Resources

Copyright, the American Association of Neurological Surgeons, September 2005.