Researchers use unique imaging technology to study changes in the brain that lead to dementia following stroke

November 26, 2000

Thanks to innovative magnetic resonance imaging technology (MRI), researchers at Rush-Presbyterian-St. Luke's Medical Center, Chicago may discover the reason why some people become demented after experiencing a stroke and others do not. Stroke is the third leading cause of death in the United States and is a leading cause of disability. About 750,000 people in the U.S. suffer a stroke each year.

Rush physicians and researchers are enrolling 110 participants in a $3 million National Institutes of Health supported study to determine why 30 percent of those who experience a stroke have cognitive problems while the others are able to function more normally. Most strokes occur when a blood clot blocks an artery that carries oxygenated blood to the brain.

A new technology using quantitative MRI analysis as well as diffusion tensor imaging will help identify risk markers in the brain. The researchers are focusing on two areas: the hippocampus, which is the section of the brain responsible for short-term memory, and the entorhinal cortex, which takes in information to other parts of the brain, including the hippocampus.

Looking at special MRIs of these areas, Rush scientists will be able to tell whether these two key areas of the brain were deteriorating before the stroke occurred, providing a key glimpse into possible risk factors for stroke.

If the deterioration in the hippocampus or entorhinal cortex was present before stroke, it may serve as a warning sign that individuals are at greater risk for post-stroke dementia and Alzheimer's or other cognitive disorders.

"My hope is that this five-year study will refine our knowledge of mechanisms and causes for dementia in stroke patients so that we can improve our stroke prevention efforts," said Dr. Philip B. Gorelick, director of the Center for Stroke Research at Rush-Presbyterian-St. Luke's Medical Center and principal investigator for the study. "We may find that risk factors for diseases like stroke are also risk factors for Alzheimer's and be able to design preventive strategies for both."

The MRIs provide a detailed, snapshot of the white matter in the brain, said Gorelick. "This white matter, or myelin, acts like insulation does to wiring - when it is intact, it allows the axons, which are the channels that information flows through in the brain, to work properly. When the insulation, or white matter, gets frayed or damaged, the channels inside them cannot function as well, leading to possible cognitive impairment."

The MRI data will then be compared with information gathered from cognitive tests designed to assess thinking and memory. Genetic factors will also be examined, he said. When appropriate, autopsies will be used to verify collected data.

Diffusion tensor imaging, which was developed by scientists at Stanford University and shared with Rush, uses a pulsing technique to capture images of water molecules flowing through the brain's axons. These images show whether the water molecules are flowing in the proper direction which gives us a hint of whether the white matter is intact or not, said Rush neuroscientist "Using quantitative MRI analysis may provide us with important information concerning areas that are critical for cognitive dysfunction that are important for dementia in either stroke or Alzheimer's Diseases," said Rush neuroscientist Leyla deToledo Morrell, PhD. "This may allow us to specify which regions of the brain and provide us with markers we can correlate with functional tests to assess risk for these dementing diseases."
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Rush University Medical Center

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