A kind of scan called an MRI is much better for diagnosing stroke than a CT scan, the American Academy of Neurology said in new guidelines released on Monday.

Magnetic resonance imaging or MRI detected strokes 83 percent of the time, compared to just 26 percent for computed tomography or CT scans, the group advised.

“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,” Dr. Peter Schellinger of the Johannes Wesling Clinical Center in Minden, Germany, who led the team writing the new guidelines, said in a statement.

CT scans are a specialized series of X-rays; MRI uses magnets and radio waves and both use computer programs to arrange the data into an image.

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

Most strokes are ischemic strokes, caused by a blood clot in the brain, and patients do far better when treated within about three hours. Hemorrhagic strokes are caused by bleeding in the brain and require completely different treatment.

Symptoms of a stroke can be subtle and can include sudden numbness or weakness of the face or a limb, sudden confusion, trouble speaking or walking or a sudden headache.

Stroke is the third leading cause of death in the United States, after heart disease and cancer.

The American Academy of Neurology is an international association of more than 22,000 neurologists and neuroscience professionals.

SOURCE: Neurology, July 2010.