Stanford researcher redefines stroke terms in push for better treatment

November 20, 2002

STANFORD, Calif. - Effective stroke treatment is dependent upon a quick diagnosis and speedy treatment, but both can be slowed by an outdated definition of a mild form of stroke called transient ischemic attack (TIA). To clarify the difference between stroke and TIA (or "mini-stroke"), a group of internationally recognized experts published a new definition in the Nov. 21 issue of the New England Journal of Medicine. The researchers hope their clarification will help improve treatment for stroke patients.

"It has been appreciated for many years that the current definition of TIA has not been appropriate," said Gregory Albers, MD, professor of neurology and neurological sciences at the Stanford School of Medicine and lead author on the paper. "This redefinition is part of a push to get stroke treated better."

Strokes are caused when a blood vessel in the brain becomes blocked, no longer delivering oxygen and nutrients to brain cells. This can lead to symptoms such as weakness or numbness on one side of the body, problems speaking or loss of vision. Under the old definition, if these symptoms last less than 24 hours, a person is considered to have suffered a TIA rather than a stroke. Symptoms that last longer than 24 hours, on the other hand, would lead to a stroke diagnosis. "The idea was that if symptoms went away within 24 hours the patient was unscathed," Albers said.

The actual difference between a TIA and a stroke is a matter of brain injury rather than an arbitrary time limit, Albers noted. In a TIA, the blood clot clears naturally before brain cells are permanently damaged. Symptoms usually last between 20 minutes and an hour; however, they can continue for many hours in some cases. In a stroke, blood-starved brain cells die, leaving the patient with permanent brain injury.

The outdated definition of TIA has misled doctors, preventing good stroke treatment. In some cases, emergency doctors may wait to see if symptoms disappear rather than offer treatment. This can delay treatment with a highly effective clot-busting drug called tPA that can dramatically improve stoke recovery when given within three hours after symptoms begin.

"What we frequently hear is, 'Why do you want to be aggressive in treating a patient who might only be having a TIA,'" said Albers. He added that this confusion contributes to the fact that only about 2 percent of people who suffer a stroke receive tPA despite its proven benefits.

The older definition has led many doctors to think of a TIA as harmless even though about 5 percent of patients who have a TIA experience a stroke within the next two days. Some insurance companies also refuse to pay for hospital admission if a patient is diagnosed with TIA, even if imaging studies reveal that brain injury - i.e. a stroke rather than a TIA - has occurred.

Albers said the 24-hour rule for defining TIA came about in the 1960s at a time when no treatments for stroke existed and there was no way to tell if a patient had permanent brain injury. "Now that we have sophisticated imaging techniques we can identify small regions of brain damage," he said. "This allows the new definition of TIA to be based on the presence of tissue injury rather than a time limit."

In the redefinition, patients who come to the emergency room with significant stroke symptoms should be assessed for brain damage. If the patient appears to be having a stroke rather than a TIA, doctors should give tPA immediately to dissolve the clot and restore blood flow to the brain.

"Part of our goal is to stimulate stroke education both in the community and for health professionals," Albers said. In many cases people never tell their physicians about symptoms that last briefly, keeping doctors from preventing a future stroke or assessing for other brain conditions. "We want the public to be aware of stroke symptoms so they know to get to a hospital immediately," Albers said. He also hopes the redefinition will help physicians and hospitals make effective stroke therapy a higher priority.
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Stanford University Medical Center integrates research, medical education and patient care at its three institutions - Stanford University School of Medicine, Stanford Hospital & Clinics and Lucile Packard Children's Hospital at Stanford. For more information, please visit the Web site of the medical center's Office of Communication & Public Affairs at http://mednews.stanford.edu.

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Stanford University Medical Center

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