Researchers here demonstrate that MRI scans of white matter in the brain can be used to visualize a form of dysfunction that is strongly associated with the near term development of dementia in patients already showing some degree of cognitive decline. Given that low cost approaches to predicting the declines of neurodegeneration earlier rather than later are still thin on the ground, possibilities such as this one are valuable indeed. The earlier the determination that dementia is ahead, the more opportunities there are to enact preventative strategies.
Neurologists can get a ballpark estimate of a patient's risk of Alzheimer's dementia using the Mini-Mental State Examination questionnaire, or by testing for the high-risk form of the gene ApoE, which increases a person's risk of Alzheimer's by up to 12-fold. Both tests were about 70 to 80 percent accurate in this study. Other assessments, such as PET scans for plaques of Alzheimer's proteins in the brain, are good at detecting early signs of Alzheimer's disease, but available to few patients. PET scans are expensive and require radioactive materials not found in a typical hospital.
In a small study, researchers have shown that MRI brain scans predict with 89 percent accuracy who would go on to develop dementia within three years. MRI brain scans are widely available and give doctors a glimpse into what's going on inside a person's brain. The researchers used a technique called diffusion tensor imaging to assess the health of the brain's white matter, which encompasses the cables that enable different parts of the brain to talk to one another. Diffusion tensor imaging is a way of measuring the movement of water molecules along white matter tracts. If water molecules are not moving normally it suggests damage to white tracts that can underlie problems with cognition.
Researchers identified 10 people whose cognitive skills declined over a two-year period and matched them by age and sex with 10 people whose thinking skills held steady. The average age of people in both groups was 73. Then, the researchers analyzed diffusion tensor MRI scans taken just before the two-year period for all 20 people. The researchers found that people who went on to experience cognitive decline had significantly more signs of damage to their white matter. The researchers repeated their analysis in a separate sample of 61 people, using a more refined measure of white matter integrity. With this new analysis, they were able to predict cognitive decline with 89 percent accuracy when looking at the whole brain. When the researchers focused on specific parts of the brain most likely to show damage, the accuracy rose to 95 percent.