THURSDAY, May 7 (HealthDay News) --"Mini-strokes" should be treated with the same urgency as a full-blown stroke, urges the American Heart Association/American Stroke Association.

That's because the risk of a major stroke after a warning stroke, known as a transient ischemic attacks (TIA), is higher than previously thought, according to a scientific statement from the groups released Thursday.

"We think a TIA should be treated as an emergency, just like a major stroke," Dr. J. Donald Easton, chairman of the clinical neurosciences department at Brown University's Alpert Medical School and the Rhode Island Hospital in Providence and chairman of the statement writing group, said in a news release from the associations.

"Because we know the high risk of a future stroke, this is a golden opportunity to prevent a catastrophic event," he said.

The statement notes that 10 percent to 15 percent of people who have a TIA have a major stroke within three months, and half of those strokes occur within 48 hours of the TIA.

The traditional clinical definition of TIA, written in the mid-1960s, is "a sudden, focal neurological deficit of presumed vascular origin lasting less than 24 hours."

The new scientific statement changes that definition of TIA to "a transient episode of neurological dysfunction caused by focal brain, spinal cord or retinal ischemia, without acute infarction."

Infarction is tissue death, the main distinction between TIA and stroke. MRI can be used to determine infarction.

"Research around the globe has shown that the arbitrary threshold based on duration of symptoms was too broad because up to half of TIAs defined this way actually caused sustained brain injury according to an MRI," Easton said.

The new scientific statement appears in the current issue of Stroke.

More information

The U.S. National Institute of Neurological Disorders and Stroke has more about transient ischemic attack.