MRI Improves Acute Stroke Diagnosis

Comparison of two imaging techniques for the emergency diagnosis of acute stroke shows that magnetic resonance imaging (MRI) can provide a more sensitive diagnosis than computed tomography (CT) for acute ischemic stroke, according to a report in The Lancet.

An MRI was better at detecting acute ischemic stroke - the most common form of stroke, which is caused by a blood clot in the brain.

The study was conducted by physicians at the National Institute of Neurological Disorders and Stroke (NINDS).

“These NIH research findings on acute stroke imaging are directly applicable to real-world clinical practice,” says National Institutes of Health (NIH) Director Dr. Elias A. Zerhouni. “The patients involved in this study were the typical cross-section of suspected stroke patients that come into emergency rooms on a daily basis.”

Test Helps Note Treatment Success

The study has good news for patients, according to Dr. Walter J. Koroshetz, NINDS deputy director.

“This study shows that approximately 25 percent of stroke patients who come to the hospital within three hours of onset, the time frame for approved clot-busting therapy, have no detectable signs of damage," says Dr. Koroshetz.

"In other words, brain injury may be completely avoided in some stroke victims by quick re-opening of the blocked blood vessel," he says.

The researchers conducted the study to determine whether MRI was superior to CT for emergency diagnosis of acute ischemic and hemorrhagic stroke (caused by bleeding into the brain).

Standard CT uses x-rays that are passed through the body at different angles and processed by a computer as cross-sectional images, or slices, of the internal structure of the body or organ.

Standard MRI uses computer-generated radio waves and a powerful magnet to produce detailed slices or three-dimensional images of body structures and nerves. A contrast dye may be used in both imaging techniques to enhance visibility of certain areas or tissues.

Study results show immediate non-contrast MRI is about five times more sensitive than and twice as accurate as immediate non-contrast CT for diagnosing ischemic stroke.

Non-contrast CT and MRI were equally effective in the diagnosis of acute intracranial hemorrhage.

Non-contrast CT has been the standard in emergency stroke treatment, primarily to exclude hemorrhagic stroke, which cannot be treated with clot-busting therapies.

“Many patients who come to hospitals with a suspected stroke ultimately have a different diagnosis," says Dr. Steven Warach, director of the NINDS Stroke Diagnostics and Therapeutic Section and senior investigator of the study.

"Most possible stroke victims are first evaluated by non-specialists, who may be reluctant to treat a patient for stroke without greater confidence in the accuracy of the diagnosis," he says.

"Our results show that MRI is twice as accurate in distinguishing stroke from non-stroke. Based on these results, MRI should become the preferred imaging technique for diagnosing patients with acute stroke.”

Better Therapy Decisions Help Patients

Study leaders hope that because of its increased diagnostic accuracy, MRI may lead to better patient outcomes and ultimately decrease the cost of stroke care, through increased use of acute treatments and earlier initiation of secondary prevention.

“Although MRI is remarkably accurate in detecting early stroke damage, it can’t substitute for a doctor’s clinical judgment in making a stroke diagnosis and deciding upon treatment,” notes Dr. Koroshetz.

“Future studies are needed to determine whether advanced contrast enhanced CT techniques can afford the same level of clinical information more quickly and with less expense," he says.

Always consult your physician for more information.