Doctors should use a diffusion MRI scan to diagnose stroke instead of a CT scan, according to a new guideline from the American Academy of Neurology. The guideline is 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, MD, with the Johannes Wesling Clinical Center in Minden, Germany.
A majority of strokes are ischemic, caused by lack of blood flow in the brain, usually due to a blockage or a blood clot. The window for treatment to reverse the damage from an ischemic stroke is measured in hours.
CT scans are a specialized kind of X-ray taken of the brain while MRI uses magnets and radio waves that show clearer images of brain tissue. Diffusion MRI measures molecular water motion in the tissue, showing 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 a person's first stroke symptom. In one large study, among others, that was reviewed for the guideline, stroke was accurately detected 83 percent of the time by MRI versus 26 percent 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," Schellinger said. "This is important because the research suggests finding lesions early may lead to better health outcomes."