DALLAS - March 9, 2004 - A widespread lack of public awareness about stroke prevents the delivery of leading-edge therapies and hampers the efforts of researchers to test the next generation of clot-busting drugs, said Dr. Hal Unwin, associate professor of neurology at UT Southwestern Medical Center at Dallas.
Last year at Parkland Memorial Hospital - the primary adult teaching hospital for UT Southwestern faculty physicians - only 19 percent of 349 patients diagnosed with the most common form of stroke arrived within three hours of the initial attack, Dr. Unwin said. Three hours is the crucial window of time in which the fast-acting, clot-busting drug called tissue plasminogen activator (tPA) must be administered. The drug dissolves blood clots in the brain, greatly reducing the risk of death or severe disability.
In June 2003 UT Southwestern launched a trial of Desmoteplase, a second-generation clot-buster made from the saliva of vampire bats that can be administered up to nine hours after the onset of a stroke. But only 16 percent of 252 stroke patients screened for the study since its inception arrived within nine hours of the onset of stroke, and of those 40 patients, none qualified for the treatment. Some arrived in time to receive tPA, and others failed to qualify because they had high blood pressure, were over 85, or had taken an anticoagulant.
"Here we have this opportunity to triple the window of time in which we can treat patients with an effective, fast-acting drug, and we haven't been able to use it in this study - largely because people don't know the signs of stroke, and they don't treat it like an emergency," Dr. Unwin said. "It's amazing the number of people we encounter who suddenly can't use their arm one night, and they'll just go to bed and hope it's better by morning."
Stroke is the third-leading cause of death and a leading cause of severe disability in the United States. It affects 750,000 Americans of all ages each year. Less than 3 percent of stroke patients nationwide receive tPA, which was refined by UT Southwestern researchers in the 1980s.
According to the American Stroke Association, 74 percent of Americans do not know the most common warning signs of stroke:
- Sudden numbness in the arm, leg or face on one or both sides of the body
- Unexpected severe headache with no apparent cause
- Sudden confusion, trouble speaking or comprehending
- Sudden vision problems, dizziness, and loss of balance or coordination
While stroke is more common in those over 50, it can happen at any age, even in children. Recognition of stroke in children has increased in recent years partly because of the widespread use of noninvasive diagnostic tests such as magnetic resonance imaging (MRI), computed tomography (CT), magnetic resonance angiography (MRA), and, in the neonatal months, cranial ultrasound studies.
In children, strokes occur most frequently during the first year of life, according to the National Institute of Neurological Disorders and Stroke. The most common cause of stroke in children is congenital heart disease.
"Stroke is still, in many environments, poorly understood and poorly treated. It really is a tragedy, and it strongly emphasizes the importance of the educational process," said Dr. Duke Samson, chairman of neurological surgery at UT Southwestern.
UT Southwestern neurologists are on call 24 hours a day to treat stroke, either at Parkland, St. Paul University Hospital or Children's Medical Center Dallas. The medical center is involved in ongoing stroke studies and is equipped with an array of high-tech tests that help to pinpoint the cause of stroke, and, in many cases, prevent future attacks. One such procedure preempts the chance of stroke from a ruptured aneurysm using a medical device smaller than a standard paper clip.
A stroke is caused when a blood vessel leading to the brain is blocked or bursts. About 83 percent of strokes are caused by blocked blood vessels and are called ischemic strokes. The remaining 17 percent are known as hemorrhagic strokes - caused by a ruptured blood vessel.
When either form of stroke occurs, part of the brain begins to die from lack of oxygen and nutrients, and the parts of the body controlled by that area of the brain are adversely affected.
Desmoteplase, the second-generation clot-buster currently undergoing clinical trials, was discovered after Mexican scientists hypothesized in the 1960s that bats must possess something that keeps blood from clotting when they extract it from prey. The specific protein responsible for the anti-clotting action was identified in the 1980s.
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