TUESDAY, Oct. 19, 2004 (HealthDayNews) -- In the critical hours after a stroke, magnetic resonance imaging (MRI) pictures of the brain give doctors more valuable information than computerized tomography (CT) scans do, a study says.
CT scans have been the standard brain-imaging technique used in emergency rooms when stroke is suspected because they can quickly show whether a brain hemorrhage has occurred, said study co-author Dr. Jeffrey F. Saver, a professor of neurology at the University of California, Los Angeles Medical Center.
But only about 15 percent of strokes result from a burst blood vessel that causes a hemorrhage, Saver added. The others are caused by ischemia, which is a blockage of an artery by a blood clot.
"MRI scans are much more informative about early ischemic injury to the brain," Saver said. "They can allow physicians to arrive at a diagnosis more quickly to select the best therapy."
That quickness was apparent during the study, the results of which appear in the Oct. 20 issue of the Journal of the American Medical Association. Both MRIs and CT images were obtained from 200 patients admitted to hospitals with signs of stroke.
The study was cut short when the analysis showed that MRIs were detecting problems that CT scans were missing, such as acute bleeding caused by ischemic damage. The MRI images showed bleeding in 71 patients, while CT scans showed them in 29 patients.
Both imaging techniques were equally effective at detecting major bleeds, which were found in 25 patients. But MRI scans showed chronic bleeds, most often very small bleeds, in 49 patients that were missed by CT scans.
The finding has already started to change medical practice, said study co-author Dr. Chelsea S. Kidwell, an associate professor of neurology at UCLA. "Already, many academic stroke centers are going both MRI and CT," she said. "Because of our study, they can be comfortable in eliminating CT."
What's missing now is evidence that use of MRIs to quickly identify the cause of stroke improves the ultimate outcomes for patients, Saver said. There are studies that show selecting patients for aggressive treatment based on MRI testing three hours or more after a stroke occurs improves the outcome, he said. Large-scale studies to show that earlier use of MRI will have the same beneficial effect are under way, Saver said.
Two other studies in the same issue of the journal focused on the clot-dissolving therapy given to patients who have ischemic strokes. A study by neurologists at the University of Western Ontario in Canada found that patients who show little improvement in the first 24 hours after clot-dissolving therapy begins are 13 times more likely to suffer a severe disability. And they are 7.5 times more likely to die three months after treatment than those who had good early responses.
And neurologists at the University of Muenster in Germany reported on a European study of more than 1,600 people who had suffered ischemic strokes. It showed that older people and those who had "disturbances of consciousness" were at greatest risk of death after clot-dissolving treatment. Doctors should give "special attention" to those patients to reduce their risk of dying, the researchers said.
More information
You can learn about the causes, symptoms and treatment of stroke from the National Institute of Neurological Disorders and Stroke.
