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Stroke and Sickle Cell Disease
What is sickle cell disease?
Sickle cell disease (SCD) is a genetic (inherited) blood disorder in which
hemoglobin, the oxygen-carrying protein in the red blood cells, is slightly
abnormal. Having red blood cells like these can restrict blood flow by
blocking small blood vessels. The body recycles these cells more rapidly
than normal red cells, which leads to severe (hemolytic) anemia. Only the
more severe forms of sickle cell-related disease are associated with stroke.
Who is at risk for stroke?
Someone with only one gene which causes SCD has sickle trait and is usually
free of symptoms because the normal hemoglobin (Hb A) counteracts the sickle
hemoglobin (Hb S). If both genes controlling hemoglobin formation are the
sickle type, the person has homozygous SCD. In rare cases, a person may have
one S-type gene but no other gene at all, referred to as sickle beta
thalassemia disease. These two types of SCD can be associated with stroke.
Children with SCD are 200 to 400 times as likely to suffer a stroke,
compared to children without SCD or congenital heart disease.
The Cooperative Study of Sickle Cell Disease (CSSCD), a large prospective
study, confirmed that stroke is a constant threat after age 2, but the
incidence is highest in the middle of a child's first 10 years of life.
About 11% of all children with homozygous SCD will develop stroke by 20
years of age.
Some characteristics of SCD are associated with an increased risk of stroke,
and include low hemoglobin, elevated white blood cell count, frequency of
acute chest syndrome, and history of transient ischemic attack.
for more information, try visiting:
http://www.healthopedia.com/sickle-cell-anemia
How many children with sickle cell disease have stroke in the United
States?
Of the 2000 children with SCD born in the US each year, about 10% will
develop stroke by adulthood. Perhaps as many as one in five will have
abnormal areas on magnetic resonance imaging scans of the brain that suggest
some stroke-like damage has occurred in the past.
What kind of stroke do children with sickle cell disease
have?
There are two kinds of strokes. A cerebral infarction is caused by a block
of blood flow which results in the starvation and death of a part of the
brain. An intracranial hemorrhage results from the rupture of a blood vessel
in or around the brain. Studies have shown that both types occur in children
with SCD, but infarcts are much more common.
What causes stroke in sickle cell disease?
The most prominent manifestation results from large artery disease. Stroke
in children with SCD is not well understood, but one theory is that stroke
usually happens when major arteries of the brain are narrowed or blocked. In
some cases, the blockage is severe enough to restrict blood flow. When the
narrowing becomes severe enough, the part of the brain supplied by that
artery is deprived of blood and oxygen, and a permanent area of brain damage
occurs.
Many patients with an infarction have abnormal cerebral blood vessels. In
general, the vessels that feed the brain (carotids and vertebrobasilar) are
normal in their cervical portions. Stenosis or occlusion, however, often
affects the distal internal carotid (dICA) and middle cerebral arteries
(MCA). In most cases the vertebrobasilar system, even if the cerebral
cranial portion, remains relatively normal.
Injury to the endothelium over time, possibly relating to red blood cell
adherence to the endothelium and circulating inflammatory factors and white
cells, may cause narrowing of vessels. The narrowing can be shown on
angiography, and when it is significant, can be detected by
TCD.
At least 20% of patients with no history of stroke, no symptoms, or readily
evident signs of brain injury, will have an abnormal MRI usually showing
small lesions in the white matter which are associated with decreased
performance in neuropsychological testing. These so-called ?silent strokes?
may also indicate an increased risk of clinically evident stroke damage.
In other cases, the arterial disease may cause clots which go further
upstream and block arteries, causing stroke. Small arteries in the brain may
also be blocked by sickled red blood cells. Rarely, stroke may be caused by
the rupture of a blood vessel, causing a brain hemorrhage.
What happens when a child with sickle cell disease has a stroke?
The symptoms of stroke and sickle cell disease are the same as in other
disorders:
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Paralysis on one side of the body
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Difficulty with speech or vision
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Numbness on one side of the body
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Sudden severe headache with possible loss of consciousness
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Seizures, particularly partial seizures.
Manifestations of a stroke depend on whether it is an infarction
or a hemorrhage. In SCD, children are most likely to have infarctions, but may
have hemorrhages, often with fatal consequences. Adults with SCD have both
infarctions and hemorrhage. Multiple strokes cause cumulative damage and can
result in severe physical and mental impairment.
What is the treatment for children with stroke? What about adults?
Children with SCD who present with acute stroke symptoms require urgent
evaluation and are usually treated with hydration and exchange transfusion.
Adults with acute stroke, including those with SCD, should be evaluated for the
use of tissue-type plasminogen activator (tPA), which can improve the outcome of
patients with ischemic stroke if they are treated within three hours of stroke
onset. In either case, a CT scan is needed to rapidly differentiate a hemorrhage
from an infarction.
Once a child has a stroke, what are the chances of another stroke?
It has been estimated that as many as two-thirds of young SCD children with
stroke will have more strokes unless treated with chronic blood transfusion.
Children with infarction, and many with hemorrhage, are put on a chronic
transfusion program to reduce the sickle hemoglobin (Hb S) to less than 30% of
total hemoglobin. With treatment, the rate of recurrence is greatly reduced. At
present, this secondary stroke prevention program has to be continued until the
problems of transfusion (e.g., iron overload) exceed the benefits of stroke
prevention. Transfusion is used less often for adults with stroke, but is still
the main treatment in SCD.
What should future parents know?
People who are planning to become parents should know whether they are carriers
of the sickle cell gene. If they are, they may want to speak to a genetic
counselor who can tell them what the chances are that their child will have
sickle cell trait or SCD. Accurate diagnostic tests and information are
available from health departments, neighborhood health centers, medical centers
and clinics that care for individuals with SCD.
For More Information Contact:
Sickle Cell Disease Scientific Research Group
Division of Blood Diseases and Resources
National Heart, Lung, and Blood Institute
6701 Rockledge Drive MSC 7950
Bethesda, MD 20892-7950
301-435-0055
The Comprehensive Sickle Cell Centers
www.rhofed.com/sickle
Sickle Cell Disease Association
of America
200 Corporate Pointe
Culver City, CA 90230-7633
1-800-421-8453 or 310-216-6363
The Sickle Cell Information Center
is an excellent Web site which is updated regularly.
More information on stroke and its warning signs can be obtained from the
American Stroke Association.