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A subarachnoid hemorrhage occurs when bleeding from a damaged blood vessel causes an accumulation of blood at the surface of the brain. This blood enters the space between the brain and the skull, and mixes with the cerebrospinal fluid that cushions the brain and spinal cord. This increases the pressure that surrounds the brain, interfering with brain function.
Incidence; Causes & Development
Subarachnoid hemorrhages affect five 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.
Several large arteries form a circle at the base of the 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 7mm or more. About 11 million people in the United States have at least one saccular aneurysm in the brain, about 25,000 to 30,000 people have a subarachnoid hemorrhage annually.
An Arteriovenous Malformation (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 are usually 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).
Most often, a subarachnoid hemorrhage happens because a bulge in the wall of an artery (a saccular aneurysm) ruptures. A subarachnoid hemorrhage also can occur because blood leaks from an abnormal tangle of blood vessels called an AVM.
In most cases, the hemorrhage develops suddenly without any specific trigger or warning. However, subarachnoid hemorrhage occasionally follows intense physical exercise.
Signs & Symptoms
Symptoms can include:- Very severe headache
- Nausea and vomiting
- Inability to look at bright light
- Stiff neck
- Dizziness
- Confusion
- Seizure
- Loss of consciousness
- Coma or death.
Diagnosis & Tests
If you have a subarachnoid hemorrhage, you probably will be ill enough that you will 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. A lumbar puncture 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: a small sample of cerebrospinal fluid is removed from your back and is examined to see if it contains blood.
Another test, called an MRI angiography, can evaluate blood flow to your brain and can be used to detect remaining aneurysms or AVM abnormalities.
You also may have an electrocardiogram (EKG). The dramatic stress on the brain during a subarachnoid hemorrhage can cause some reflex changes in your heart's circulation, so an EKG test may be abnormal.
Treatment & Prevention
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. This can result in a lower, safer amount of pressure around the brain. A change in the blood's carbon dioxide level after the heavy breathing causes a decrease in the amount of blood flowing into the brain, so there is less pressure overall. 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 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 blood can be pumped 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 may be used to prevent 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, this can repair an aneurysm. An AVM sometimes can be obliterated by a carefully directed beam of radiation, can be removed through surgery, or blood flow through the area can be blocked with the injection of a gluelike substance. Often, a combination of treatments is used.
Early help by 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 maximize recovery.
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 that is not causing any symptoms involves significant risks, and most aneurysms never cause serious bleeding. This screening may make sense for some people who have two or more close relatives who have had bleeding in or around the brain from an aneurysm. Because aneurysm screening is controversial, you should consider the risks of surgery carefully with your doctor before you request a screening test.
Prognosis; Complications; Seek medical attention if
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%.
One out of five survivors of subarachnoid hemorrhage has another bleeding episode within 14 days if their aneurysm or AVM is not treated quickly. If the aneurysm or AVM is not treated, 50% rebleed within six 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.
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 persisting neurological disabilities.
Subarachnoid hemorrhages account for about 7% of all strokes.
Call for emergency help immediately whenever a friend or family member shows any unexpected neurological symptoms, especially if that person losses consciousness or suddenly develops a seizure. Also, call your doctor promptly if you develop a severe headache and you are vomiting. Less intense headaches also 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 still important to discuss this with your doctor. Sometimes blood leaks briefly from a blood vessel six 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.
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Signs, symptoms & indicators of Subarachnoid Hemorrhage:
KEY | | Weak or unproven link |  | | Strong or generally accepted link |
GLOSSARY
Aneurysm
Localized enlargement of an artery.
Arterial (Arteries, Artery)
Blood that leaves the heart. When it leaves the right ventricle, it is venous blood; and when it leaves the left ventricle, through the aorta, it is fresh and oxygenated. After it has passed out to the capillaries and started to return, it is venous blood.
Computerised Tomography (CAT Scan, Computed Tomography, Computerized Axial Tomography, CT Scan)
A scanning procedure using X-rays and a computer to detect abnormalities of the body's organs. This technique provides cross-sectional images of body organs, which is much clearer than those provided by conventional X-rays.
Electrocardiogram (ECG, EKG)
A test that shows a tracing of the electrical conduction of the heart.
Electrolyte (Electrolytes)
An element or compound that, when melted or dissolved in water or other solvent, breaks up into ions and is able to carry an electric current.
Hemorrhage (Hemorrhaging)
Profuse blood flow.
Magnetic Resonance Imaging (MRI)
A technique used in diagnosis that combines radio waves and magnetic forces to produce detailed images of the internal structures of the body.
Millimeter (Millimeters, mm)
A metric unit of length equaling one thousandth of a meter, or one tenth of a centimeter. There are 25.4 millimeters in one inch.
Nausea
Symptoms resulting from an inclination to vomit.
Seizure (Seizures)
While there are over 40 types of seizure, most are classed as either partial seizures which occur when the excessive electrical activity in the brain is limited to one area or generalized seizures which occur when the excessive electrical activity in the brain encompasses the entire organ. Although there is a wide range of signs, they mainly include such things as falling to the ground; muscle stiffening; jerking and twitching; loss of consciousness; an empty stare; rapid chewing/blinking/breathing. Usually lasting from between a couple of seconds and several minutes, recovery may be immediate or take up to several days.
Sodium
An essential mineral that our bodies regulate and conserve. Excess sodium retention increases the fluid volume (edema) and low sodium leads to less fluid and relative dehydration. The adult body averages a total content of over 100 grams of sodium, of which a surprising one-third is in bone. A small amount of sodium does get into cell interiors, but this represents only about ten percent of the body content. The remaining 57 percent or so of the body sodium content is in the fluid immediately surrounding the cells, where it is the major cation (positive ion). The role of sodium in the extracellular fluid is maintaining osmotic equilibrium (the proper difference in ions dissolved in the fluids inside and outside the cell) and extracellular fluid volume. Sodium is also involved in nerve impulse transmission, muscle tone and nutrient transport. All of these functions are interrelated with potassium.
Spasm
Involuntary contraction of one or more muscle groups.
Spinal Tap (Lumbar Puncture)
Despite the discomfort felt by many over this procedure, spinal taps are actually very simple procedures from the doctor's standpoint. Because the fluid that coats and flows through the brain also flows down into the spinal cord, the spinal fluid reflects what is occurring in the brain. A spinal tap involves: numbing the skin over the lower part of the spine with an injection or cream; sterilizing the area; having the patient curl up on his side while being held securely; passing a needle through the skin at a large space in between two of the lower vertebrae (the needle does NOT pass through bone); slowly advancing the needle until it "pops" through the lining of the spinal canal into an area of spinal fluid (the needle does NOT go into the spinal cord where the nerves are because the spinal cord stops further up the spine: the bottom of the spine simply contains a reservoir of spinal fluid); spinal fluid will flow out through the needle and the doctor will collect it and send it to the lab. Once the needle is pulled out, the hole seals up rapidly.
Stroke (Stroke-Type Event)
A sudden loss of brain function caused by a blockage or rupture of a blood vessel that supplies the brain, characterized by loss of muscular control, complete or partial loss of sensation or consciousness, dizziness, slurred speech, or other symptoms that vary with the extent and severity of the damage to the brain. The most common manifestation is some degree of paralysis, but small strokes may occur without symptoms. Usually caused by arteriosclerosis, it often results in brain damage.
Last updated: Oct 08, 2008
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