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Brain Plaques Don’t Indicate Alzheimer’s Onset

By Stephen Luntz

The debate about the causes of Alzheimer’s disease has turned again, with the publication in PLoS ONE of evidence that plaque only appears after memory loss has begun.

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The finding suggests that plaque is not a useful test for the early stages of Alzheimer’s, and could have a substantial influence on the search for cures.

“Ever since Alois Alzheimer first described this disease in 1906, plaque has been regarded as the definitive Alzheimer’s diagnosis,” said project leader Dr Bryce Vissel of the Garvan Institute of Medical Research. Since plaque could not be detected until after death, the timing of its appearance was hard to determine but was thought to precede, or at least coincide with, early dementia symptoms.

However, plaque detection is now possible using positron emission tomography (PET) in living people. This was thought to offer potential for early Alzheimer’s diagnosis but Vissel says: “Our study suggests that this method may not be accurate in earlier disease stages”.

Instead, Vissel found that nerve cell loss and inflammation appear earlier. His work was done with a mouse model, requiring painstaking counting of the number of nerve cells and measurement of inflammation at five different ages of mice with a gene for Alzheimer’s disease. Two other groups released similar conclusions from different methodologies this year.

With billions of dollars of research funding chasing a method of preventing or slowing the development of plaques, so far with little result, some researchers are suggesting that the...

The full text of this article can be purchased from Informit.