MRI may help determine time of stroke onset

Brain MRI could expand the number of stroke patients eligible for a potentially life-saving treatment, according to a new study, published online and in the December issue of Radiology.

In the study, Dr. Catherine Oppenheim and her team of 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.

“As many as a quarter of all stroke patients cannot be given tissue plasminogen activator (tPA) because they wake up with stroke symptoms or are unable to tell their doctor when their stroke began,” said Oppenheim, a professor of radiology at Université Paris Descartes in France.

The 130 patients in the study included 77 men and 53 women (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 different types of MRI data on the patients, including fluid-attenuated inversion recovery, diffusion-weighted imaging and apparent diffusion coefficient ratios.

Using the MRI data alone, the radiologists were able to 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,” she said.

Using MRI to determine the duration of a stroke would change the way stroke is managed in the emergency setting, Oppenheim said.

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

Clinical trials are the next step necessary to validate the use of MRI as a surrogate marker of stroke duration, Oppenheim said.