What is a brain aneurysm?

A brain (cerebral) aneurysm is a bulging, weak area in the wall of an artery that supplies blood to the brain. In most cases, a brain aneurysm causes no symptoms and goes unnoticed. In rare cases, the brain aneurysm ruptures, releasing blood into the skull and causing a stroke.

When a brain aneurysm ruptures, the result is called a subarachnoid hemorrhage. Depending on the severity of the hemorrhage, brain damage or death may result.

The most common location for brain aneurysms is in the network of blood vessels at the base of the brain called the circle of Willis.

What causes a brain aneurysm?

A person may inherit the tendency to form aneurysms, or aneurysms may develop because of hardening of the arteries (atherosclerosis) and aging. Some risk factors that can lead to brain aneurysms can be controlled, and others can't. The following risk factors may increase your risk of developing an aneurysm or, if you already have an aneurysm, may increase your risk of it rupturing:1

• Family history. People who have a family history of brain aneurysms are twice as likely to have an aneurysm as people who don't.
• Previous aneurysm. About 20% of patients with brain aneurysms have more than one.
• Gender. Women are twice as likely to develop a brain aneurysm or to suffer a subarachnoid hemorrhage as men.
• Race. African Americans have twice as many subarachnoid hemorrhages as whites.
• Hypertension. The risk of subarachnoid hemorrhage is greater in people with a history of high blood pressure (hypertension).
• Smoking. In addition to being a cause of hypertension, the use of cigarettes may greatly increase the chances of a brain aneurysm rupturing.
What are the symptoms?

Most brain aneurysms cause no symptoms and may only be discovered during tests for another, usually unrelated, condition. In other cases, an unruptured aneurysm will cause problems by pressing on areas within the brain. When this happens, the person may suffer from severe headaches, blurred vision, changes in speech, and neck pain, depending on the areas of the brain that are affected and the severity of the aneurysm. If you have any of the following symptoms or notice them in someone you know, see a health professional immediately.

Symptoms of a ruptured brain aneurysm often come on suddenly. They may include:

• Sudden, severe headache (sometimes described as a "thunderclap" headache that is very different from any normal headache).
• Neck pain.
• Nausea and vomiting.
• Sensitivity to light.
• Fainting or loss of consciousness.
• Seizures.
How is a brain aneurysm diagnosed?

Because unruptured brain aneurysms often do not cause any symptoms, many are discovered in people who are being treated for a different condition.

If your health professional believes you have a brain aneurysm, you may have the following tests:

• Computed tomography (CT) scan. A CT scan can help identify bleeding in the brain.
• Computed tomography angiography (CTA) scan. CTA is a more precise method of evaluating blood vessels than a standard CT scan. CTA uses a combination of CT scanning, special computer techniques, and contrast material (dye) injected into the blood to produce images of blood vessels.
• Magnetic resonance angiography (MRA). Similar to a CTA, MRA uses a magnetic field and pulses of radio wave energy to provide pictures of blood vessels inside the body. As with CTA and cerebral angiography, a dye is often used during MRA to make blood vessels show up more clearly.
• Cerebral angiography. During this X-ray test, a catheter is inserted through a blood vessel in the groin or arm and moved up through the vessel into the brain. A dye is then injected into the cerebral artery. As with the above tests, the dye allows any problems in the artery, including aneurysms, to be seen on the X-ray. Although this test is more invasive and carries more risk than the above tests, it is the best way to locate small (less than 5 mm) brain aneurysms.
Sometimes a lumbar puncture may be used if your health professional suspects that you have a ruptured cerebral aneurysm with a subarachnoid hemorrhage.

How is it treated?

Your doctor will consider several factors before deciding the best treatment for you. Factors that will determine the type of treatment you receive include your age, the size of the aneurysm, any additional risk factors, and your overall health.

Because the risk of a small (less than 10 mm) aneurysm rupturing is low and surgery for a brain aneurysm is often risky, your health professional may want to continue to observe your condition rather than perform surgery. However, if your aneurysm is large or causing pain or other symptoms, or if you have had a previous ruptured aneurysm, your health professional may recommend surgery.

The following surgeries are used to treat both ruptured and unruptured brain aneurysms:

• Coil embolization. During this procedure, a small tube is inserted into the affected artery and positioned near the aneurysm. Tiny metal coils are then moved through the tube into the aneurysm, relieving pressure on the aneurysm and making it less likely to rupture. This procedure is less invasive and is believed to be safer than surgical clipping, although it may not be as effective at reducing the risk of a later rupture. It should be done in a large hospital where many such procedures are performed. • Surgical clipping. This surgery involves placing a small metal clip around the base of the aneurysm to isolate it from normal blood circulation. This decreases the pressure on the aneurysm and prevents it from rupturing. Whether this surgery can be done depends on the location of the aneurysm, its size, and your general health.
Some aneurysms bulge in such a way that the aneurysm has to be cut out and the ends of the blood vessel stitched together, but this is very rare. Occasionally the artery is not long enough to stitch together, and a piece of another artery has to be used.

Aneurysms that have bled are very serious and in many cases lead to death or disability. Management includes hospitalization and intensive care to relieve pressure in the brain and maintain breathing and vital functions (such as blood pressure) and treatment to prevent rebleeding.

Treatments and drugs
Here are the general guidelines for treating abdominal aortic aneurysms:

• Small aneurysm. If you have a small aortic abdominal aneurysm — about 1.6 inches, or 4 centimeters (cm), in diameter or smaller — and you have no symptoms, your doctor may suggest a watch-and-wait (observation) approach, rather than surgery. In general, surgery isn't needed for small aneurysms because the risk of surgery outweighs the risk of rupture.

If you choose this approach, your doctor will monitor your aneurysm with periodic ultrasounds, usually every six to 12 months and encourage you to report immediately if you start having abdominal tenderness or back pain - potential signs of a dissection or rupture.

• Medium aneurysm. A medium aneurysm measures between 1.6 and 2.2 inches (4 and 5.6 cm). It's less clear how the risks of surgery versus waiting stack up in the case of a medium-size aortic abdominal aneurysm. You'll need to discuss the benefits and risks of waiting versus surgery and make a decision with your doctor.

• Large, fast-growing or leaking aneurysm. If you have an aneurysm that is large (larger than 2.2 inches, or 5.6 cm) or growing rapidly (more than 0.5 cm over six months), you'll probably need surgery. In addition, a leaking, tender or painful aneurysm requires treatment. There are two types of surgery for abdominal aortic aneurysms.

Open-abdominal surgery to repair an abdominal aortic aneurysm involves removing the damaged section of the aorta and replacing it with a synthetic tube (graft), which is sewn into place, through an open-abdominal approach. With this type of surgery, it will likely take you several months to fully recover.

• Large, fast-growing or leaking aneurysm. If you have an aneurysm that is large (larger than 2.2 inches, or 5.6 cm) or growing rapidly (more than 0.5 cm over six months), you'll probably need surgery. In addition, a leaking, tender or painful aneurysm requires treatment. There are two types of surgery for abdominal aortic aneurysms.

Open-abdominal surgery to repair an abdominal aortic aneurysm involves removing the damaged section of the aorta and replacing it with a synthetic tube (graft), which is sewn into place, through an open-abdominal approach. With this type of surgery, it will likely take you several months to fully recover.

Endovascular surgery is a less invasive procedure sometimes used to repair an aneurysm. Doctors attach a synthetic graft to the end of a thin tube (catheter) that's inserted through an artery in your leg and threaded up into your aorta. The graft — a woven tube covered by a metal mesh support — is placed at the site of the aneurysm and fastened in place with small hooks or pins. The graft reinforces the weakened section of the aorta to prevent rupture of the aneurysm.

Recovery time for people who have endovascular surgery is shorter than for people who have open-abdominal surgery — about one or two weeks compared with six weeks for open surgery.

The options for treatment of your aneurysm will depend on a variety of factors, including location of the aneurysm, your age, kidney function and other conditions that may increase your risk for surgery or endovascular repair

Understanding aneurysms
A true aneurysm is a bulge in all three layers of a blood vessel wall. If there is a bulge in some portion of the blood vessel wall but not in all three layers (commonly seen in aneurysms formed as a result of injury), it is a pseudoaneurysm.

The aorta could be described as a smooth tube that is fairly constant in diameter throughout its course from the heart to the abdomen until it divides. An aneurysm occurs when a portion of the aorta bulges more than 3 centimeters in diameter. After it initially forms, it is likely to increase in size as you age.

As an aneurysm expands, the tension on the blood vessel wall increases. This in turn causes the aneurysm to expand further, which puts even more tension on the wall. This cycle continues, and the larger the aneurysm gets, the greater the chances that it will grow larger and eventually burst.

Understanding that aneurysms expand is a key to managing them: the larger they become, the higher the rate of rupture, and the more important it is to treat them.

The location of the aneurysm is also important. Aneurysms can be located in any blood vessel in the body. Aortic aneurysms can be found in the thoracic portion, the abdominal portion, or both. The treatment, surgical approach, and outcome of aneurysms involving the thorax and the abdomen can be quite different.

For example, if an abdominal aortic aneurysm is found below the kidneys, the aorta is cross-clamped below the arteries that supply blood to the kidneys (renal arteries), allowing a normal blood flow and a less risky operation. On the other hand, if the aneurysm is located above the kidneys, the clamp may have to be placed above the renal arteries and thus blood flow to the kidneys is limited. This increases the risk for kidney failure.

Another distinction should be drawn between aneurysms based on their cause. While most arise from chronic changes in the arterial wall and take many years to develop, a small percentage are caused by infection or inflammation. These are called inflammatory aneurysms. While the surgical principles are the same for all aneurysms, inflammatory aneurysms may be more severe and occasionally involve other blood vessels and adjacent organs.

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Endoscopic technology has allowed surgeons to look at traditional methods of treating vascular diseases with an eye toward innovation. The Skull Base Institute has pioneered Endoscopic Brain Aneurysm Clipping, revolutionizing the way that vascular surgery is performed with less disruption of normal brain tissue, less painful recovery, and a rapid return to daily activities.

OVERVIEW

A cerebral aneurysm is an abnormally dilated segment of a blood vessel surrounding the brain. In some cases, the entire blood vessel widens and expands resembling a balloon-like structure. Cerebral aneurysms are said to occur in 3-5% of the general population, are more common in patients older than 30, and are almost twice as common in women than men.

Nearly ¼ of all cerebrovascular deaths are due to ruptured aneurysms. The annual incidence of cerebral aneurysm rupture is approximately 7/100,000 persons. The peak incidence of aneurysm rupture occurs around age 50 - 60, although rare cases may occur in children and patients over 75. The risk of aneurysm rupture is approximately 0.05 - 2% per year depending on the size and characteristics of the aneurysm.

Causes
The exact cause of many cerebral aneurysms is not completely clear. In general, aneurysms are thought to arise from a weakened area in the wall of a blood vessel. Some aneurysms may occur as congenital defects in the lining of blood vessels in the body; resulting in continued aneurysm enlargement throughout one's lifetime. There appears to be a familial component to the development of aneurysms, as they are much more common in first degree relatives, especially siblings. On rare occasions, multiple occurrences are reported.

Several factors can induce weakening of the blood vessel wall including: infection, trauma, brain tumor, and arteriovenous malformation (abnormal blood vessel development). Factors, which have been shown to increase the risk of aneurysm rupture include: smoking, excessive alcohol consumption, and arteriosclerosis.
Symptoms
Occasionally, an enlarging aneurysm can cause symptoms through the compression of surrounding neurologic structures (i.e. visual changes, seizures, facial pain, etc). Unfortunately, symptoms frequently do not appear until the aneurysm has ruptured. The rupture of a cerebral aneurysm is usually sudden and occurs without any warning. Symptoms of a ruptured aneurysm may include any of the following: loss of consciousness, severe headache with nausea or vomiting, stiff neck, difficulty moving any part of the body, numbness or decreased sensation in any part of the body, blurred vision, drooping eyelids, seizure, and/or a change in mental status.

Once an aneurysm ruptures, blood accumulates between the brain and the subarachnoid space (a thin wall surrounding the brain), thus resulting in a subarachnoid hemorrhage (SAH). As blood collects in this space, it compresses and damages the surrounding brain tissue. The tissue injury Causes the surrounding blood vessels to be susceptible to vasospasm. Vasospasm is an abnormal constriction of the blood vessels of the brain, which can result in additional tissue damage through diminished blood flow to the brain. The combined effect of bleeding and vasospasm can result in serious neurologic impairment or even death.

Diagnosis
A thorough neurologic exam is performed to assess mental status and determine specific deficits. In the past, examination of the cerebrospinal fluid provided evidence of bleeding in the subarachnoid space. Today, 3-dimensional spiral CT angiography or magnetic resonnance angiography (MRA) of the brain are the standard tests used to diagnose cerebral aneurysms. Video x-rays of blood vessels using injected dye (Cerebral Angiography) provides even more detailed images of the blood vessels in the brain, often visualizing the exact location of the aneurysm.

Treatment
Cerebral aneurysms, once ruptured require urgent medical attention. The goal of treating patients suffering from rupture of a cerebral aneurysm is to control the immediate symptoms and prevent further bleeding. Upon arrival to the hospital, a patient's vital signs, such as respiration, blood pressure and circulation are stabilized. Depending on the location, size and extent of bleeding the Neuroradiologist using catheters similar to the ones used to perform the cerebral angiogram can occasionally occlude the aneurysm and stop the bleeding using small metal coils or other inert material (endovascular embolization). However, this method only achieves adequate aneurysm occlusion in 50-70% of patients.

Either due to aneurysm size, location, or inadequate endovascular embolization many ruptured aneurysms require immediate surgical intervention. The goal of the operation is to place a surgical clip at the base of the aneurysm to control the bleeding and eliminate the risk of re-bleeding. Standard supportive treatments following aneurysm rupture include: bed rest, mild sedation, medications to prevent seizures and help reduce vasospasm. A Doppler ultrasound device is used to monitor the degree of vasospasm. Complications such as re-bleeding, severe vasospasm, and brain swelling are the major causes of morbidity and mortality after aneurysm rupture.

Prognosis
About 15% of patients with ruptured aneurysms die before reaching the hospital, whereas an additional 20-40% do not survive despite the very best in current medical care. Therefore, early diagnosis and proper treatment are crucial for a good prognosis. Research has shown that several factors contribute to an improved prognosis including: an effective patient transfer system, rapid diagnosis with immediate access to CT/MRI imaging, 24 hour availability of highly qualified surgeons familiar with both the surgical treatment of cerebral aneurysms/SAH as well as the most modern medical treatment both pre- and post-operatively.

To avoid the devastating consequences of aneurysm rupture, surgeons often recommend surgical clipping or endovascular embolization of asymptomatic aneurysms.