In the first study, lead researcher Liana Apostolova and colleagues tracked 169 people over three years who had been diagnosed with mild cognitive impairment (MCI), a condition that causes memory problems greater than those expected for an individual's age — but not the personality or cognitive changes that define Alzheimer's. They found that after three years, those who went on to be diagnosed with Alzheimer's disease showed a ten to 30 percent greater atrophy in two specific locations within the brain's hippocampus, a part of the brain known to be critical for long-term memory.
In the second study, the researchers looked at ten cognitively normal elderly people and compared their brain scans with those of seven other elderly people who were later diagnosed with MCI and then Alzheimer's. Again, they found that the group that went on to be diagnosed with Alzheimer's showed the same pattern of atrophy in the same regions of the hippocampus.
This shows, Apostolova said, that excess atrophy is present in cognitively normal individuals who are predestined to develop MCI. Further, that atrophy ultimately cascades across the entire hippocampus of the brain, leading to Alzheimer's disease.
"We feel this is an important finding because it is in living humans," said Apostolova, senior author of both papers. "Now we have a sensitive technique that shows the 'invisible' — that is, the progression of a disease before symptoms appear."
Apostolova noted that the degree of atrophy is not easily visible in the brain scans and that very sensitive techniques are required to show its progression. "We can't see the pathologic changes, but we clearly see the neurodegenerative atrophy associated with MCI and AD, and how it spreads through the hippocampus," she said. "This is exactly what a biomarker, being an indirect measure of disease progression, is supposed to do."
COMPAMED.de; Source: University of California, Los Angeles (UCLA), Health Sciences