Time is important - so some good news....

MRI images may pinpoint time of stroke:

Researchers found that MRI data could accurately determine if patients had experienced stroke symptoms within a three-hour period or less, which would allow the use of a clot-busting drug that works best if administered within that window of time. Tissue plasminogen activator, known as tPA, can dramatically reverse stroke symptoms in those whose strokes are caused by blood clots and blockages, which account for an estimated 85 percent of all strokes.

Strokes strike about 795,000 Americans each year, killing 137,000, according to the U.S. Centers for Disease Control and Prevention. The condition is a leading cause of serious, long-term disability in the United States.

"A tool that can estimate the age of stroke would be of great value in cases of unknown stroke onset time," said lead researcher Dr. Catherine Oppenheim, professor of radiology at Universite Paris Descartes in France. "This concerns as many as a quarter of all stroke patients who cannot be given tPA because they wake up with stroke symptoms or are unable to say when their stroke began."