Sunday, April 24, 2011

In a recent Neurology article (2011;76:1395-1402) a study showed that the measurement of the thickness of several areas of the brain’s gray matter may predict who will develop and who will not Alzheimer’s disease (AD) years later and are presently cognitively normal. MRI scans were done on a series of patients, measurement made of various regions of their cortex, and followed for 10 year. 55% in the lowest third of cortical thickness developed AD dementia during follow-up. In contrast, no individual with the highest cortical thickness at baseline developed AD during follow-up.

" Richard B. Lipton, MD, of Albert Einstein College of Medicine in the Bronx, New York, who was not involved in the study, said, "The most interesting finding is that persons in the highest third of cortical thickness never developed AD. If these findings are replicated, this would mean that we can identify a sizeable group of older adults and reassure them that they are very unlikely to develop AD.

"In a world where fear of AD is an enormous problem, this kind of reassurance would be valuable to older adults and their families. In addition, these individuals could be excluded from studies of preventive intervention since it is impossible to improve on such low risk," Dr. Lipton said.

"The study is limited by the small sample size, but the results are exciting because of their strength and consistency," Dr. Lipton commented. "It is worth noting," he said, "that even in those with thinnest cortices, AD did not develop for 4 years. This is likely related to the rigorous exclusion of dementia in the sample, but it suggests that if the goal is short-term prediction of risk, for prevention trials, for example, this is not the way to go," he said.
Dr. Lipton also noted that cortical thickness could be a lifelong marker of brain reserve, a factor that protects against AD.

"Alternatively, cortical thinning could be a manifestation of unfolding disease, which could produce neuronal loss as illness develops, well before it becomes diagnosable," he said. "These 2 factors could each separately contribute to the findings."

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