Based on the old knowledge of these episodes, known medically as transient ischemic attacks (TIAs), doctors often wait them out. However, the experts, writing in tomorrow's issue of The New England Journal of Medicine, say most TIAs are emergencies and should be treated as such.
Strokes are caused either by a blocked blood vessel in the brain or a blood vessel that has burst and is causing excessive bleeding. In either case, parts of the brain stop receiving blood and are deprived of oxygen and other vital nutrients, resulting in brain damage. A TIA, on the other hand, is usually caused by a small blot clot that clears up naturally before any brain damage can occur.
Currently, if stroke symptoms last 24 hours or less, the event is considered a TIA. However, this definition was developed in 1965, before sensitive imaging tests and effective treatments were available for stroke.
"One of the problems with the old definition is that [doctors] felt they could wait around to see if stroke symptoms were getting better," says Dr. Gregory Albers, a professor of neurology and neurological sciences at Stanford School of Medicine and one of the experts proposing a new definition for TIA. "But if you have symptoms that last for 60 minutes or more, it's highly likely that it's a stroke. And the sooner you start treatment for stroke, the better the response."
Stroke is the third leading cause of death in the United States, killing about 167,000 people every year, according to the National Stroke Association. Until the mid-1990s there was little physicians could do to treat strokes caused by blocked blood vessels. Now, a drug called tissue plasminogen activator (tPA) can dissolve the blood clot, which can prevent much of the brain damage and death associated with stroke. However, tPA is effective only if given within the first three hours after the onset of symptoms, and Albers says getting the medication before 90 minutes has elapsed is even better.
One of the biggest reasons Albers and other stroke experts from across the United States propose changing the definition of TIA is so that tPA can be administered more quickly, rather than waiting for 24 hours to see if the symptoms resolve on their own.
Albers points out that during the clinical trials of tPA, half of the patients received the medication and half received a placebo. Researchers later discovered that in the untreated group, only 2 percent of the patients had any significant recovery on their own after having symptoms for 24 hours.
"TIAs are very brief. They don't last for hours and hours," Albers says. "It's extremely unlikely to be a TIA after an hour."
The proposed new definition of a TIA is a short period of neurological dysfunction and no evidence of a blood clot on CT or MRI scans done soon after the symptoms begin. If the symptoms last more than a short time, such as an hour, or there is evidence of a blockage in a blood vessel on the imaging tests, it should be considered a stroke, says the expert group.
Symptoms of TIA and stroke are the same: sudden weakness or numbness on one side of the body, trouble speaking, sudden loss of vision, and loss of balance or coordination. In a TIA, these symptoms should disappear quickly. In a stroke, they will not go away without immediate medical intervention. That doesn't mean, however, that if you have these symptoms and they disappear in 20 minutes that you don't need to get to the emergency room.
"TIA is an urgent medical situation that needs to be reported right away," explains Albers. "TIAs are associated with a high risk of stroke. One in 20 people with a TIA will have a stroke within 48 hours," he adds.
Dr. Keith A. Siller, a neurologist at New York University Medical Center, agrees that people, and insurance companies, need to take TIAs more seriously.
"TIA is a strong warning sign for a future stroke," Siller says. "TIA is like the chest pain before a heart attack. It's a sign of underlying vascular disease."
He says the proposed new definition of TIA is something that stroke neurologists already know and practice, but says it might be helpful for other physicians who might hold back on giving tPA because they're not sure if it's a stroke or a TIA and they're concerned about tPA's side effects.
What To Do
For more information on TIA, visit the National Institute of Neurological Disorders and Stroke.