Subarachnoid Hemorrhage
What
is a Subarachnoid Hemorrhage?
A subarachnoid hemorrhage is
bleeding onto the surface of the brain, most often caused by a break in
a blood vessel at the base of the brain. A blood vessel usually breaks
at a weak spot called an aneurysm.
When a blood supply to part of the brain is reduced or completely blocked, a stroke may occur. That is, the part of the brain deprived of blood dies and can no longer function.
How
does it occur?
A subarachnoid hemorrhage often
occurs without warning and is life threatening. It is most common in the
35 to 65 year old age group. About 5% of the population has aneurysms.
Normal blood pressure can cause the weak spot to balloon and break. High
blood pressure strains the weak spot even more. Although an aneurysm can
occur in any blood vessel, aneurysms are most commonly found at the base
of the brain and in the main artery coming out of the heart. Aneurysms
that occur at the base of the brain are usually caused by a defect in
an artery that the person has had since birth.
In a subarachnoid hemorrhage, the aneurysm most often breaks at the base of the brain and the blood flows into the subarachnoid space, mixing with the fluid that surrounds the brain and spinal cord (cerebrospinal fluid).
What
are the symptoms?
Before rupturing, aneurysms
usually produce no symptoms or warning signs. Rarely, symptoms that may
occur before the aneurysm ruptures include:
- headache.
- Weakness on one side of your body.
- Numbness.
- Tingling.
- Speech disturbance.
- Double vision that does not go away.
When the aneurysm ruptures, in about half the cases, the person experiences an excruciating headache and falls unconscious almost immediately. In others, a headache develops but the person remains conscious. Some people have no headache and become unconscious quickly without warning.
How
is it diagnosed?
To diagnose a subarachnoid
hemorrhage, you will probably have a brain scan. The doctor may do a lumbar
puncture to see how much blood has mixed with the cerebrospinal fluid.
To determine where the blood vessel broke, the doctor may do an angiogram.
During this procedure, dye is injected into your bloodstream and x-rays
are taken. The dyed blood vessels then appear on the x-ray film.
How
is it treated?
After a hemorrhage occurs,
usually very little can be done to prevent disability or even death. The
aim of treatment is to stop the bleeding and damage to the brain and reduce
the risk of recurrence. Treatment and monitoring during the 3 weeks immediately
following the hemorrhage are important since that is the period when complications
and rerupture are most likely to occur. Medication may be prescribed to
prevent seizures, and sedatives may be used to aid relaxation. Absolute
bedrest is necessary to prevent a rerupture. Sometimes a surgeon can repair
a broken blood vessel depending on the location and size of the aneurysm.
If unbroken aneurysms are discovered, the doctor may suggest surgery to
repair these before they break. Multiple aneurysms are present in as many
as 20% of cases.
How
long will the effects last?
If the hemorrhage is large,
the person may die immediately. In cases involving smaller hemorrhages
the person will regain consciousness, but may be left with some brain
damage. Approximately one third of all cases recover completely.
How
can I take care of myself?
Follow your doctor's instructions
regarding treatment and frequency of medical visits. Do not smoke, avoid
caffeinated beverages, and have your blood pressure checked regularly.
How
can I prevent a subarachnoid hemorrhage?
Because many of these aneurysms
have been present since birth, prevention is difficult. However, you can
be aware if you have a family history of strokes and aneurysms and monitor
your blood pressure. If an aneurysm is discovered early, the doctor may
be able to repair the weak spot and prevent a hemorrhage from occurring.
Reviewed by UMHS Cardiovascular Center May 2005