Subarachnoid Hemorrhage

What Is It?

A subarachnoid hemorrhage is bleeding from a damaged artery at the surface of the brain. This bleeding causes a sudden, very severe headache, and it is a medical emergency. A subarachnoid hemorrhage is a type of stroke, and it can damage the brain.

Blood from a subarachnoid hemorrhage pulses into the space between the brain and the skull. It mixes with the cerebrospinal fluid that cushions the brain and spinal cord. As blood flows into the cerebral spinal fluid, it increases the pressure that surrounds the brain. The increased pressure can interfere with brain function.

In the days that immediately follow the bleeding, chemical irritation from clotted blood around the brain can cause one or several brain arteries to go into spasm. An artery spasm can damage brain tissue, resulting in a stroke. This process can cause new symptoms during the first few days after a subarachnoid hemorrhage, such as weakness on one side, speech difficulties or loss of consciousness.

Each year, about 30,000 people in North America have a subarachnoid hemorrhage. Most often, a subarachnoid hemorrhage happens because a bulge in the wall of an artery ruptures. The saclike bulge is called a saccular aneurysm. A subarachnoid hemorrhage also can occur because blood leaks from an abnormal tangle of blood vessels called an arteriovenous malformation (AVM).

Ruptured Aneurysm

Several large arteries form a circle at the base of your brain. When a subarachnoid hemorrhage is caused by a ruptured saccular aneurysm, the aneurysm usually is located where a blood vessel branches from one of these large arteries. About 20% of patients who have had a subarachnoid hemorrhage have multiple aneurysms. Although it is not possible to predict whether an aneurysm will rupture, an aneurysm is more likely to rupture when it has a diameter of 7 millimeters or more. In most cases, a person who has a brain aneurysm never has a symptom related to it. Of the 11 million people in the United States who have at least one saccular aneurysm in the brain, onlly about 1 out of every 400 of them have a subarachnoid hemorrhage each year.

Leaking AVM

An AVM is a tangled, abnormal mesh of blood vessels that connects an artery and a vein in the brain. AVMs form accidentally prior to birth. An AVM can form almost anywhere in the brain or spinal cord, but they usually are near the back of the brain. AVMs can appear in several generations of the same family and are more common in men. Bleeding from an AVM most often occurs between the ages of 10 and 30. If an AVM is too deep to cause bleeding onto the outer surface of the brain (a subarachnoid hemorrhage), it can cause bleeding inside the brain itself (intracerebral hemorrhage).

Subarachnoid hemorrhages account for about 7% of all strokes. They affect 5 to 10 out of every 100,000 people in the United States, most commonly between ages 35 and 60. About 85% of these patients have saccular aneurysms.

Symptoms

The symptoms of a subarachnoid hemorrhage can include:

• Very severe, sudden headache (Some people say the start of this headache is like a thunderclap.)
• Nausea and vomiting
• Inability to look at bright light
• Stiff neck
• Dizziness
• Confusion
• A seizure
• Loss of consciousness
• Coma or death

If you have only a small subarachnoid hemorrhage, you may have several of these symptoms, particularly a severe headache that starts suddenly. However, your symptoms may improve on their own. This can be a critical warning sign, called a sentinel headache. People who have a small subarachnoid hemorrhage may have a second hemorrhage within the next week if they do not get medical treatment.

In the several days that follow a subarachnoid hemorrhage, it is possible to develop more typical symptoms of a stroke from damage to specific areas of the brain. Examples of these symptoms include:

• Weakness, paralysis or numbness of one side or one part of the body
• Difficulty speaking
• Difficulty walking
• Coma

Diagnosis

If you have a subarachnoid hemorrhage, you will be ill enough that you need be evaluated in an emergency room. The doctor will do a physical examination, including a neurological examination, and will check to see if your neck movement is limited or uncomfortable, which can be a sign that there is an irritant such as blood in the spinal fluid.

One of two brain imaging tests will be used: either a computed tomography (CT) scan or magnetic resonance imaging (MRI) scan. CT scans provide an image more quickly.

A lumbar puncture, also called a spinal tap, can confirm that you have a subarachnoid hemorrhage even when the hemorrhage is too small to appear on a CT scan. This test also can test whether you have meningitis, an infection that can cause similar symptoms. During a lumbar puncture, a small sample of cerebrospinal fluid is removed through a needle inserted into your back. This fluid is examined to see if it contains blood.

Two other tests, called brain angiography and MRI angiography, can evaluate blood flow patterns in your brain. One of these tests can be used to detect an aneurysm or AVM abnormality.

You also may have an electrocardiogram (EKG). The dramatic stress on the brain during a subarachnoid hemorrhage can trigger chemical changes within your heart muscle. These changes can stress the heart muscle, and may cause a heart attack, even if your heart arteries are not narrowed by atherosclerosis.

Expected Duration

For those who survive a subarachnoid hemorrhage, recovery is slow. Most people do not recover complete functioning within months of a subarachnoid hemorrhage, and up to 50% of people who survive subarachnoid hemorrhage will have neurological disabilities that last much longer or become permanent.

Prevention

It is almost impossible to prevent subarachnoid hemorrhage caused by an aneurysm or AVM, because these blood vessel abnormalities usually do not cause any symptoms before the hemorrhage occurs. Smoking has been shown to increase the risk of forming an aneurysm, so avoiding smoking may prevent some cases of hemorrhagic stroke.

Some people have proposed screening tests, such as MRI angiography, that would identify aneurysms before they cause a problem. However, this idea has been impractical for most people, because surgery to remove an aneurysm can leave you with decreased function after your recovery. For most people, this is a risk that is not worth taking, since most aneurysms never cause serious bleeding. Screening and surgery are not recommended for people who have a single close relative who has a brain aneurysm or a subarachnoid hemorrhage. Screening and surgery may make sense for people who have two or more close relatives who have had bleeding, since such a family is at particularly high risk. Because aneurysm screening is controversial, you should consider the risks of surgery carefully with your doctor before you ask for a screening test.

Treatment

When a large hemorrhage occurs in or around the brain, the entire brain is in danger because of increasing pressure within the skull. Much of the emergency treatment for hemorrhagic stroke involves measuring and lowering this pressure. A mechanical ventilator frequently is used to cause someone who has had a subarachnoid hemorrhage to breathe faster, which lowers the carbon dioxide level in the blood and causes less blood to flow into the brain. This lowers the pressure around the brain. The sugar mannitol is used as a medicine injected into a vein to treat a brain hemorrhage because it pulls brain fluid into the bloodstream, which also lowers pressure around the brain. If necessary, blood that has collected can be drained through a hole made in the skull bone.

If the pressure in and around the brain is very high, a person's blood pressure must be allowed to stay higher than normal so that the body can pump blood through this elevated pressure zone. Medicines that lower blood pressure may be stopped or reduced.

Many doctors routinely prescribe medication to protect against seizures, and this medicine may be continued for six months or more.

Subarachnoid hemorrhages commonly cause arteries nearest to the site of bleeding to spasm and become narrower, so medicines such as nimodipine may be used to partially protect you against this reaction. A subarachnoid hemorrhage also causes shifts in the level of electrolytes, especially sodium, in the blood. You may be given medicines or intravenous (in a vein) fluid to keep sodium at a normal level.

If bleeding occurred because of an abnormally formed blood vessel, then surgery may be needed to prevent a hemorrhage in the future. If a surgeon is able to place a surgical clip on the blood vessel, this can repair an aneurysm. An AVM sometimes can be destroyed by a carefully directed beam of radiation or can be removed through surgery. In some cases, blood flow through the area can be blocked with the injection of a gluelike substance. Often, a combination of treatments is used.

Early counseling from an occupational therapist and physical therapist is helpful. These therapists are professionals who can assist a patient to work around a new disability and to regain strength after brain injury. Commonly, hospitalization is followed by a period of residence at a rehabilitation center, where additional intensive therapy may be provided. The goal of rehabilitation is to help the patient recover as much as possible.

When To Call A Professional

Call for emergency help immediately whenever a friend or family member shows any unexpected symptoms that suggest to you they may be having a subarachnoid hemorrhage, especially if that person loses consciousness or suddenly develops a seizure. Call your doctor promptly or have a friend take you to the emergency room if you develop a severe headache and you are vomiting. Less-intense headaches should be evaluated by your doctor if you have them often or if they are accompanied by symptoms such as nausea, vomiting, weakness or numbness in any part of the body.

If you have a sudden, very severe headache but it goes away, it is critically important to discuss this with your doctor. Sometimes blood leaks briefly from a blood vessel 6 to 20 days before a subarachnoid hemorrhage occurs. The headache this leak causes is called a sentinel headache. Your doctor may be able to provide treatment that can prevent more serious bleeding.

Prognosis

Many patients with a subarachnoid hemorrhage do not survive long enough to reach a hospital. Of those who do, about 50% die within the first month of treatment. However, in patients with subarachnoid hemorrhages resulting from AVMs, the risk of death is only about 15%.

Among patients who survive a bleeding aneurysm, up to 50% suffer long-term neurological problems. One out of 5 survivors of subarachnoid hemorrhage has another bleeding episode within 14 days if the aneurysm or AVM is not treated quickly. If the aneurysm or AVM is not treated, 50% rebleed within 6 months. When surgery is used to clip bleeding aneurysms, there is a good chance of success, but there is also a 5% risk of death or long-term disability.

Additional Info

National Institute of Neurological Disorders and Stroke

P.O. Box 5801

Bethesda, MD 20824

Phone: (301) 496-5751

Toll-Free: (800) 352-9424

TTY: (301) 468-5981

http://www.ninds.nih.gov/

National Stroke Association

9707 E. Easter Lane

Englewood, CO 80112

Phone: (303) 649-9299

Toll-Free: 800-787-6537

Fax: (303) 649-1328

http://www.stroke.org/