MRI May Determine Stroke Onset Time, Treatment Options

Magnetic resonance imaging of the brain could increase the number of stroke patients eligible for a potentially life-saving treatment, according to a study in the December issue of Radiology.

The Patient:

Some patients who suffer an acute ischemic stroke, when a blood clot or other obstruction blocks blood flow in the brain, can be treated with a drug called tissue plasminogen activator, or tPA, that dissolves the clot and restores blood flow.

However, the clot-busting drug can only be administered within four and a half hours of a stroke. Any time longer than that and the drug can cause bleeding in the brain.

"As many as a quarter of all stroke patients cannot be given tPA because they wake up with stroke symptoms or are unable to tell their doctor when their stroke began," said lead researcher Catherine Oppenheim, MD, professor of radiology at Université Paris Descartes in France.

The Stats:

The American Stroke Association says strokes are the third leading cause of death in the U.S. behind diseases of the heart and cancer. Approximately 795,000 Americans suffer a new or recurrent stroke each year.

Oppenheim and her researchers reviewed data from consecutive patients with acute ischemic stroke treated at Sainte-Anne Hospital in Paris between May 2006 and October 2008. The time of stroke onset was well defined in all patients and each underwent MRI within 12 hours.

The Study:

The 130 patients in the study included 77 men and 53 women with a mean age 64.7. Of those, 63 patients underwent MRI within three hours of stroke onset and 67 were imaged between three and 12 hours after stroke onset.

The radiologists analyzed three different types of MRI data on the patients:

1. Fluid-attenuated inversion recovery
2. Diffusion-weighted imaging
3. Apparent diffusion coefficient ratios

Using the MRI data alone, the radiologists could predict with greater than 90% accuracy which patients had experienced stroke symptoms for longer than three hours.

"When the time of stroke onset is unknown, MRI could help identify patients who are highly likely to be within the three-hour time window when tPA is proven effective and approved for use," Oppenheim says. Adding that using MRI to determine the duration of a stroke would change the way stroke is managed in the emergency setting.

"With the use of MRI, all stroke patients could be managed urgently, not just those patients with a known onset of symptoms," she adds.

Oppenheim says clinical trials are needed to validate the use of MRI as a surrogate marker of stroke duration.

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