Brain Scan May Be First-Ever Test for Alzheimer's Nov. 7, 2001 -- In the largest study of its kind to date, an international team of researchers has found that a specialized brain scan can accurately predict whether early symptoms of memory loss will become full-blown dementia down the road.

Right now, Alzheimer's disease is diagnosed as the person continues to lose more and more mental ability. But the only way to know for sure if someone has had Alzheimer's is to do an autopsy on the brain and look for the markers of the disease -- telltale clumps of gnarled protein called "tangles and plaques."

The positron emission tomography, or PET, scan is not new. And scientists already knew that in the brains of people with worsening dementia, there are very specific and significant changes in metabolism, or the way the brain uses nutrients such as sugar. Early in the course of illness, when treatment might be able to slow the loss of brain function, the PET scan picks up these changes.

Before this study, however, there simply weren't enough people who'd had both a PET scan when symptoms first began and an autopsy when they died. So there wasn't enough before-and-after information that would help scientists draw any firm conclusions about what the PET scan results truly meant.

Now, an international research group, led by Daniel H.S. Silverman, MD, PhD, of UCLA School of Medicine, has collected enough information to show that these particular changes, which PET scanning can detect soon after someone begins showing signs of memory loss, are indeed a strong indicator that further, potentially devastating mental decline is not far off.

The study is published in the Nov. 7 issue of the Journal of the American Medical Association.

They looked at nearly 300 people seeking medical help for recent problems with concentration and thinking, or changes in behavior or personality. About 150 received a brain PET scan, and were then followed for an average of three years to see if symptoms worsened. Another 150 had the initial scan and also underwent an autopsy when they died.