A brain aneurysm (AN-yoo-riz-um) — also known as a cerebral aneurysm or intracranial aneurysm — is a bulge or ballooning in a blood vessel in the brain. An aneurysm often looks like a berry hanging on a stem.
Experts think brain aneurysms form and grow because blood flowing through the blood vessel puts pressure on a weak area of the vessel wall. This can increase the size of the brain aneurysm. If the brain aneurysm leaks or ruptures, it causes bleeding in the brain, known as a hemorrhagic stroke.
Most often, a ruptured brain aneurysm occurs in the space between the brain and the thin tissues covering the brain. This type of hemorrhagic stroke is called a subarachnoid hemorrhage.
Brain aneurysms are common. But most brain aneurysms aren't serious, especially if they're small. Most brain aneurysms don't rupture. They usually don't cause symptoms or cause health problems. In many cases, brain aneurysms are found during tests for other conditions.
However, a ruptured aneurysm quickly becomes life-threatening and requires medical treatment right away.
If a brain aneurysm hasn't ruptured, treatment may be appropriate in some cases. Treatment of an unruptured brain aneurysm may prevent a rupture in the future. Talk with your health care provider to make sure you understand the best options for your specific needs.
A sudden, severe headache is the key symptom of a ruptured aneurysm. This headache is often described by people as the worst headache they've ever experienced.
In addition to a severe headache, symptoms of a ruptured aneurysm can include:
In some cases, an aneurysm may leak a slight amount of blood. When this happens, a more severe rupture often follows. Leaks may happen days or weeks before a rupture.
Leaking brain aneurysm symptoms may include:
An unruptured brain aneurysm may not have any symptoms, especially if it's small. However, a larger unruptured aneurysm may press on brain tissues and nerves.
Symptoms of an unruptured brain aneurysm may include:
Seek immediate medical attention if you develop a:
If you're with someone who complains of a sudden, severe headache or who loses consciousness or has a seizure, call 911 or your local emergency number.
Brain aneurysms are caused by thinning artery walls. Aneurysms often form at forks or branches in arteries because those areas of the vessels are weaker. Although aneurysms can appear anywhere in the brain, they're most common in arteries at the base of the brain.
Several factors can contribute to weakness in an artery wall. These factors may increase the risk of a brain aneurysm or aneurysm rupture.
Some of these risk factors develop over time. But some conditions present at birth can increase the risk of developing a brain aneurysm.
Risk factors include:
Some types of aneurysms may occur after a head injury or from certain blood infections.
There are some factors that make it more likely an aneurysm will rupture. They include:
When a brain aneurysm ruptures, the bleeding usually lasts only a few seconds. However, the blood can cause direct damage to surrounding cells and can kill brain cells. It also increases pressure inside the skull.
If the pressure becomes too high, it may disrupt the blood and oxygen supply to the brain. Loss of consciousness or even death may occur.
Complications that can develop after the rupture of an aneurysm include:
A sudden, severe headache or other symptoms that could be related to a ruptured aneurysm require testing. Tests can determine whether you've had bleeding into the space between your brain and surrounding tissues. This type of bleeding is known as subarachnoid hemorrhage. The tests also can determine if you've had another type of stroke.
You also may be given tests if you show symptoms of an unruptured brain aneurysm. These symptoms may include pain behind the eye, changes in vision or double vision.
Screening tests and procedures used to diagnose and detect brain aneurysms include:
CT scan. This specialized X-ray is usually the first test used to detect bleeding in the brain or another type of stroke. The test produces images that are 2D slices of the brain.
A CT angiogram can create more-detailed images of the arteries providing blood flow in the brain. The test involves injecting dye that makes it easier to observe blood flow. It also can detect the presence of an aneurysm.
Lumbar puncture, known as a spinal tap. If you've had a subarachnoid hemorrhage, there will most likely be red blood cells in the fluid surrounding your brain and spine. This fluid is called cerebrospinal fluid. If you have symptoms of a ruptured aneurysm but a CT scan doesn't show evidence of bleeding, a test of your cerebrospinal fluid can help make a diagnosis.
The procedure to draw cerebrospinal fluid from your back with a needle is called a lumbar puncture.
MRI. This imaging test uses a magnetic field and radio waves to create detailed images of the brain, either 2D images or 3D images. The images can show if there's bleeding in the brain.
A type of MRI that captures images of the arteries in detail is called MR angiography. This type of MRI can detect the size, shape and location of an unruptured aneurysm.
Cerebral angiogram. During this procedure, a thin, flexible tube called a catheter is used. The catheter is inserted into a large artery, usually in the groin or the wrist. The catheter threads past your heart to the arteries in your brain. A special dye injected into the catheter travels to arteries throughout your brain.
A series of X-rays can then reveal details about the conditions of your arteries and detect an aneurysm. A cerebral angiogram — also called a cerebral arteriogram — is usually used when other diagnostic tests don't provide enough information.
The use of imaging tests to screen for unruptured brain aneurysms is generally not recommended unless you're at high risk. Talk to your health care provider about the potential benefit of a screening test if you have:
Most aneurysms don't rupture. And for many people, an unruptured aneurysm never causes symptoms. But if the aneurysm ruptures, several factors may affect the outcome, which is known as the prognosis. They include:
About 25% of people who experience a ruptured aneurysm die within 24 hours. Another 25% have complications that lead to death within six months.
There are two common treatment options for repairing a ruptured brain aneurysm. In some cases, these procedures may be considered to treat an unruptured aneurysm. However, the known risks may outweigh the potential benefits for people with some unruptured aneurysms.
Flow diversion is a newer endovascular treatment option for treatment of a brain aneurysm. The procedure involves placing a stent in the blood vessel to divert blood flow away from the aneurysm. The stent that's placed is called a flow diverter.
With less blood flow going to the aneurysm, there's less risk of rupture. It also allows the body to heal. The stent prompts the body to grow new cells that seal the aneurysm.
Flow diversion may be particularly useful in larger aneurysms that can't be treated with other options.
A neurosurgeon or interventional neuroradiologist will likely work with your neurologist to recommend treatment. Treatment is based on the size, location and overall appearance of the brain aneurysm. They also may consider factors such as your ability to undergo a procedure.
Other methods for treating ruptured brain aneurysms are aimed at relieving symptoms and managing complications.
Calcium channel blockers prevent calcium from entering cells of the blood vessel walls. These medicines may lessen the risk of having symptoms from the narrowing of blood vessels, known as vasospasm. Vasospasm may be a complication of a ruptured aneurysm.
One of these medicines, nimodipine (Nymalize), has been shown to reduce the risk of delayed brain injury caused by insufficient blood flow. This can happen after subarachnoid hemorrhage from a ruptured aneurysm.
Ventricular or lumbar draining catheters and shunt surgery can lessen pressure on the brain from excess cerebrospinal fluid. Fluid can build up after a ruptured aneurysm. A catheter may be placed in the spaces that are filled with fluid inside the brain. Or it can be placed in the area surrounding the brain and spinal cord. The catheter drains the excess fluid into an external bag.
Sometimes a shunt system is placed. A shunt system is a flexible silicone rubber tube and a valve that creates a drainage channel. The drainage channels starts in the brain and ends in the abdominal cavity.
A surgical clip, an endovascular coil or a flow diverter can be used to seal off an unruptured brain aneurysm. This can help prevent a future rupture. However, the risk of rupture is extremely low in some unruptured aneurysms. In these cases, the known risks of the procedures may outweigh the potential benefits.
A neurologist working with a neurosurgeon or interventional neuroradiologist can help you determine whether surgical or endovascular treatment is appropriate for you.
Factors to consider in making treatment recommendations include:
If you have high blood pressure, talk to your health care provider about medicine to manage the condition. If you have a brain aneurysm, proper control of blood pressure may lower the risk of rupture.
In addition, if you smoke cigarettes, talk with your care provider about strategies to stop smoking. Cigarette smoking is a risk factor for formation, growth and rupture of the aneurysm.
If you have an unruptured brain aneurysm, you may lower the risk of rupture by making these lifestyle changes:
The Brain Aneurysm Foundation offers information on connecting with support groups in many states and in other countries.
Brain aneurysms are often detected after they've ruptured and become medical emergencies. However, a brain aneurysm may be detected when you've undergone head-imaging tests for another condition.
If such test results indicate you have a brain aneurysm, you'll need to discuss the results with a specialist in brain and nervous system disorders. These specialists include neurologists, neurosurgeons and neuroradiologists.
To make the best use of your time with your health care provider, you may want to prepare a list of questions, such as:
Your neurologist, neurosurgeon or neuroradiologist may ask you the following questions to help determine the best course of action:
