Aneurysms

A cerebral aneurysm (also known as an intracranial or intracerebral aneurysm) is a weak or thin spot on a blood vessel in the brain that balloons out and fills with blood. The bulging aneurysm can put pressure on a nerve or the surrounding brain tissue. It may also leak or rupture, spilling blood into the surrounding tissue. This is called a hemorrhage. Some cerebral aneurysms, particularly those that are very small, do not bleed or cause other problems. Cerebral aneurysms can occur anywhere in the brain, but most are located along a loop of arteries that run between the underside of the brain and the base of the skull.

Aneurysms may burst and bleed into the brain, causing serious complications, including hemorrhagic stroke, permanent nerve damage and sometimes they can be fatal. Once it has burst, the aneurysm may burst again and bleed into the brain, and additional aneurysms may also occur. More commonly, rupture may cause a subarachnoid hemorrhage– bleeding into the space between the skull bone and the brain. A delayed but serious complication of subarachnoid hemorrhage is hydrocephalus, in which the excessive buildup of cerebrospinal fluid in the skull dilates fluid pathways called ventricles that can swell and press on the brain tissue. Another delayed postrupture complication is vasospasm, in which other blood vessels in the brain contract and limit blood flow to vital areas of the brain. This reduced blood flow can cause stroke or tissue damage.

There are three types of cerebral aneurysm:

• A saccular aneurysm is a rounded or pouch-like sac of blood that is attached by a neck or stem to an artery or a branch of a blood vessel. Also known as a berry aneurysm (because it resembles a berry hanging from a vine), this is the most common form of cerebral aneurysm and is typically found on arteries at the base of the brain. Saccular aneurysms occur most often in adults.
• A lateral aneurysm appears as a bulge on one wall of the blood vessel
• A fusiform aneurysm is formed by the widening along all walls of the vessel.

Aneurysms are also classified by size:

• Small aneurysms are less than 11 millimeters in diameter (about the size of a large pencil eraser)
• Larger aneurysms are 11-25 millimeters (about the width of a dime)
• Giant aneurysms are greater than 25 millimeters in diameter (more than the width of a quarter).

Brain aneurysms can occur in anyone, at any age. They are more common in adults than in children and slightly more common in women than in men. Children and adults with certain inherited disorders are also at higher risk.

All cerebral aneurysms have the potential to rupture and cause bleeding within the brain. The incidence of reported ruptured aneurysm is about 10 in every 100,000 persons per year (about 30,000 individuals per year in the U.S.), most commonly in people between ages 30 and 60 years. Possible risk factors for aneurysms seen in children are severe head trauma and infection.

Cerebral aneurysms can be congenital, resulting from an abnormality in an artery wall that occurs before a baby is born. Cerebral aneurysms are also more common in people with certain genetic diseases, such as connective tissue disorders like Marfan syndrome and polycystic kidney disease, and certain circulatory disorders, such as arteriovenous malformations (snarled tangles of arteries and veins in the brain that disrupt blood flow).

Other causes include trauma or injury to the head, high blood pressure, infection, tumors, atherosclerosis (a blood vessel disease in which fats build up on the inside of artery walls) and other diseases of the vascular system, cigarette smoking, and drug abuse. Aneurysms that result from an infection in the arterial wall are called mycotic aneurysms.

Cancer-related aneurysms are often associated with tumors of the head and neck.

Most cerebral aneurysms do not show symptoms until they either become very large or burst. Small, unchanging aneurysms generally will not produce symptoms, whereas a larger aneurysm that is steadily growing may press on tissues and nerves. Symptoms may include pain above and behind the eye; numbness, weakness, or paralysis on one side of the face; dilated pupils; and vision changes. When an aneurysm hemorrhages, an individual may experience a sudden and extremely severe headache, double vision, nausea, vomiting, stiff neck, and/or loss of consciousness. Adults usually describe the headache as "the worst headache of my life" and it is generally different in severity and intensity from other headaches people may experience. Children may express their pain differently. "Sentinel" or warning headaches may result from an aneurysm that leaks for days to weeks prior to rupture. Only a minority of individuals have a sentinel headache prior to aneurysm rupture. If your child complains of head pain or cries with pain, or if you notice any changes in facial expression or eye movement, it is very important to contact your doctor immediately. If your child is experiencing an aneurysm, emergency surgery may just save a life.

Other signs that a cerebral aneurysm has burst include nausea and vomiting associated with a severe headache, a drooping eyelid, sensitivity to light, and change in mental status or level of awareness. Some individuals may have seizures. Individuals may lose consciousness briefly or go into prolonged coma. Again, if your child is experiencing this "worst headache," especially when it is combined with any other symptoms, you should seek immediate medical attention.

Most cerebral aneurysms go unnoticed until they rupture or are detected by brain imaging that may have been obtained for another condition. If your child does have an aneurysm, several diagnostic methods are available to provide information about the aneurysm and the best form of treatment.

• Angiography is a dye test used to analyze the arteries or veins. An intracerebral angiogram can detect the degree of narrowing or obstruction of an artery or blood vessel in the brain, head, or neck, and can identify changes in an artery or vein such as a weak spot like an aneurysm. It is used to diagnose stroke and to precisely determine the location, size, and shape of a brain tumor, aneurysm, or blood vessel that has bled. This test is usually performed in a hospital angiography suite. Following the injection of a local anesthetic, a flexible catheter is inserted into an artery and threaded through the body to the affected artery. A small amount of contrast dye (one that is highlighted on x-rays) is released into the bloodstream and allowed to travel into the head and neck. A series of X-rays is taken and changes, if present, are noted.
• Computed tomography (CT) of the head is a fast, painless, noninvasive diagnostic tool that can reveal the presence of a cerebral aneurysm and determine, for those aneurysms that have burst, if blood has leaked into the brain. This is often the first diagnostic procedure ordered by your doctor if he or she suspects a rupture. X-rays of the head are processed by a computer as two-dimensional cross-sectional images, or "slices," of the brain and skull. Occasionally a contrast dye is injected into the bloodstream prior to scanning. This process, called CT angiography, produces sharper, more detailed images of blood flow in the brain arteries. CT is usually conducted at a testing facility or hospital outpatient setting.
• Magnetic resonance imaging (MRI) uses computer-generated radio waves and a powerful magnetic field to produce detailed images of the brain and other body structures. Magnetic resonance angiography (MRA) produces more detailed images of blood vessels. The images may be seen as either three-dimensional pictures or two-dimensional cross-slices of the brain and vessels. These painless, noninvasive procedures can show the size and shape of an unruptured aneurysm and can detect bleeding in the brain.
• Cerebrospinal fluid analysis may be ordered if a ruptured aneurysm is suspected. Following application of a local anesthetic, a small amount of this fluid (which protects the brain and spinal cord) is removed from the subarachnoid space–located between the spinal cord and the membranes that surround it–by a spinal needle and tested to detect any bleeding or brain hemorrhage. In individuals with suspected subarachnoid hemorrhage, this procedure is usually done in a hospital.

In addition, the doctor will ask you and, when possible, your child to describe the symptoms, when they started and how long they lasted. The doctor will also examine your child and take a complete medical history, including a family medical history.

Not all cerebral aneurysms burst. If your child is diagnosed with very small aneurysms, they may be monitored to detect any growth or onset of symptoms and to ensure aggressive treatment of coexisting medical problems and risk factors.

It is important to note that, like your child, each case is unique, and considerations for treating an unruptured aneurysm include the type, size, and location of the aneurysm; risk of rupture; the age and health of your child, as well as any recent head injuries, diseases or disorders, personal and family medical history and, of course, risk of treatment. Your neurology team will discuss all options and risks with you prior to treatment.

Two surgical options are available for treating cerebral aneurysms and when it comes to performing them, you can trust that our specialists are among the best in the nation. However it is important to note that any surgery, and especially brain surgery, can carry some risk to your child (such as possible damage to other blood vessels, the potential for aneurysm recurrence and rebleeding, and the risk of post-operative stroke).

• Microvascular clipping involves cutting off the flow of blood to the aneurysm. Under anesthesia, a section of the skull is removed and the aneurysm is located. The neurosurgeon uses a microscope to isolate the blood vessel that feeds the aneurysm and places a small, metal, clothespin-like clip on the aneurysm's neck, halting its blood supply. The clip remains in the person and prevents the risk of future bleeding. The skull section is then replaced and the scalp is closed. Clipping has been shown to be highly effective, depending on the location, shape, and size of the aneurysm. In general, aneurysms that are completely clipped surgically do not return.
• A related procedure is an occlusion, in which the surgeon clamps off (occludes) the entire artery that leads to the aneurysm. This procedure is often performed when the aneurysm has damaged the artery. An occlusion is sometimes accompanied by a bypass, in which a small blood vessel is surgically grafted to the brain artery, rerouting the flow of blood away from the section of the damaged artery.

Endovascular embolization is an alternative to surgery. Once your child has been anesthetized, the doctor inserts a hollow plastic tube (a catheter) into an artery (usually in the groin) and threads it, using angiography, through the body to the site of the aneurysm. Using a guide wire, detachable coils (spirals of platinum wire) are passed through the catheter and released into the aneurysm. The coils fill the aneurysm, block it from circulation, and cause the blood to clot, which effectively destroys the aneurysm. The procedure may need to be performed more than once during your child's lifetime.

After treatment, your child will remain in the medical center until the bleeding stops. In addition, underlying conditions, such as high blood pressure, will be treated. Any other treatments your doctor recommends will be based on your child's symptoms and may include anticonvulsants to prevent seizures and analgesics to treat headache. Vasospasm can be treated with calcium channel-blocking drugs and sedatives may be ordered if your child is restless to help keep him or her as still as possible during the recovery stage.

Several months following the rupture, a shunt may be surgically inserted into a ventricle if the buildup of cerebrospinal fluid is causing harmful pressure on surrounding tissue in your child's brain. Depending on the type and severity of your child's aneurysm, rehabilitative, speech, and occupational therapy may be needed to help him or her regain lost function and learn to cope with any permanent disability. Your neurology team will work with you and your family to determine the best course of action to restore your child's quality of life, now and in the future.