MRI Better Than CT Scans at Diagnosing Stroke

Physicians should use a diffusion magnetic resonance imaging (MRI) scan to diagnose stroke instead of a computed tomography (CT) scan, according to a new guideline.
The guideline was issued from the American Academy of Neurology (Saint Paul, MN, USA) and was published in the July 13, 2010, issue of Neurology, the medical journal of the American Academy of Neurology. “While CT scans are currently the standard test used to diagnose stroke, the Academy’s guideline found that MRI scans are better at detecting ischemic stroke damage compared to CT scans,” said lead guideline author Peter Schellinger, M.D., with the Johannes Wesling Clinical Center (Minden, Germany).

Diffusion MRI measures molecular water motion in the tissue, revealing where water diffusion is restricted and therefore brain damage has occurred. According to the guideline, diffusion MRI should be considered more useful than a CT scan for diagnosing acute ischemic stroke within 12 hours of an individual’s first stroke symptom. In one large study, among others, that was reviewed for the guideline, stroke was accurately detected 83% of the time by MRI versus 26% of the time by CT.

“Specific types of MRI scans can help reveal how severe some types of stroke are. These scans also may help find lesions early,” Dr. Schellinger said. “This is important because the research suggests finding lesions early may lead to better health outcomes.”

Moreover, the guideline found MRI scans more effectively detected lesions from stroke and helped identify the severity of some types of stroke or diagnose other medical conditions with similar symptoms. Dr. Schellinger reported that studies have validated the importance of using MRI in emergency rooms but said reservations still exist surrounding the use of stroke MRI scans in clinical settings. “This guideline gives doctors clear direction in using MRI first, ultimately helping people get an acute stroke diagnosis and treatment faster. However, one situation in which CT may still be used first is when a person needs an emergency injection of drug therapy [also known as intravenous thrombolytic therapy] to break up blood clots, if MRI is not immediately available, to avoid delays in starting this treatment. MRI can be added later if more information is needed. Otherwise, MRI should be used first.”

The American Academy of Neurology, an association of more than 22,000 neurologists and neuroscience professionals, is focused on promoting the highest quality patient-centered neurologic care.