Symptoms of a stroke include sudden onset of weakness or numbness on one side of the body, sudden trouble seeing, inability to talk or understand what people are saying, loss of ability to walk or loss of balance and severe headache.

Those statistics highlight the importance of immediate action when the first symptoms of a stroke appear. They were calculated by Dr. Jeffrey L. Saver, a professor of neurology at the University of California, Los Angeles. The dramatic sequence is published in the Dec. 9 issue of Stroke.

The calculation of damage was made possible by three different lines of research pursued in the past decade, Saver said.

"One is brain imaging, which allows us to measure precisely the size of a typical stroke," he said. "The second is stroke treatment, which has given us the first good evidence of how long it takes a stroke to evolve in humans. The third is quantitative neurostereology, a three-dimensional cell-counting technique that gives the first good evidence of the loss of brain circuitry."

Quick Treatment

The good news is that this steady loss of brain cells can be curtailed through quick treatment, Saver said. A powerful clot-dissolving drug called tissue plasminogen activator (tPA) can effectively reduce long-term disability if given within three hours. Other treatments include anticoagulant drugs and surgery.

Without treatment, Saver estimated, a piece of brain the size of a pea will die every 12 minutes. While a small group of brain cells will die immediately when their blood supply is cut off, the surrounding cells suffer moderate loss of blood flow, and there is "a brief window of opportunity to intervene," he said.

Saver's work provides "very good calculations to bring home the message that every minute of a stroke, a person is losing millions of brain cells," said Dr. Mark J. Alberts, a professor of neurology at Northwestern University, and a spokesman for the American Heart Association.

Symptoms of Stroke

The association has mounted a campaign to alert people to the symptoms of stroke, Alberts said. These include sudden onset of weakness or numbness on one side of the body, sudden trouble seeing, inability to talk or understand what people are saying, loss of ability to walk or loss of balance and severe headache.

Those symptoms often make it impossible for the sufferer to take action, so the responsibility falls on those who notice the problem, he said.

"When these symptoms occur, call 911 immediately and take the person to the nearest appropriate hospital," Alberts said.

More information: The symptoms of a stroke and what to do about them are described in detail by the American Heart Association.