When scientists look under the microscope at the brains of very elderly patients who have died, some confusing patterns are seen. Some patients who had healthy memory and thinking show many of the findings often seen in patients with Alzheimer disease (AD). These are called plaques and tangles. This is confusing because plaques and tangles are not always seen in normal patients but are more common in patients with AD. At the same time, some patients with significant dementia have very few of these brain changes. Brain researchers wonder how memory and brain function stay healthy in patients even though their brains show problems seen in AD.
A new study reported by Erten-Lyons and coauthors tries to answer this question (Neurology2009;72:354–360). They compared the brains of patients with AD to another group that had similar findings under the microscope but had normal thinking and memory. They asked, “What protects those patients whose thinking remains normal?” The investigators looked for differences in the medical histories and brain examinations of these two groups. They also looked at differences in the size of some brain areas using MRI scans that were taken when the patient was living. Along with the MRIs, other changes were considered, like age, sex, and timing of the MRIs. The authors' idea was that plaques and tangles might be necessary to cause AD, but that there might be some important reasons why some patients did not get AD. They thought that patients with healthy brains might be able to lose some brain function but have enough reserve that these changes did not result in dementia. The authors were also interested in other factors that might show why these patients seemed to be protected.
WHAT WAS THE MAIN FINDING?
Surprisingly, the two groups were not …
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