By measuring subtle changes in brain structure through sophisticated brain imaging techniques, the progression of Alzheimer’s disease can be predicted, according to a series of research studies conducted by Liana Apostolova, assistant clinical professor of neurology at the University of California, Los Angeles (UCLA) and colleagues.
The first study, which appeared in the Jan. 28 online edition of Human Brain Mapping, utilized a hippocampal segmentation technique for analyzing brain MRI scans in which the researchers observed two areas within the hippocampus (a portion of the brain critical for long-term memory): the cornu ammonis (CA1) and the subiculum. The authors sought to determine if atrophy in the living brain could predict an individual’s progression from mild cognitive impairment (MCI), a condition causing memory problems greater than those expected for an individual's age, to Alzheimer’s.
Apostolova and colleagues created binary maps of the hippocampuses of 169 study participants who had been diagnosed with MCI and scanned each patient at the beginning of the study, and once again at a three-year follow-up mark. Researchers noted a 10 to 30 percent greater atrophy finding in two specific locations within the brain's hippocampus in patients who were diagnosed with Alzheimer’s at the three-year follow-up scan.
"We feel this is an important finding because it is in living humans," said Apostolova. "Now we have a sensitive technique that shows the 'invisible'—that is, the progression of a disease before symptoms appear.”
While the first study sought to observe atrophy of the hippocampus in general, the second study, which was published in the online edition of Neurobiology of Aging, tracked atrophy progression from the CA1 as it spread to the subiculum based on the original study’s findings.
"In looking at the longitudinal changes, we could see there was definitive evidence of a progression from the CA1 to the subiculum region, and on to the other regions of the hippocampus," Apostolova said.
The researchers utilized a cohort of 10 cognitively normal elderly people and seven other elderly people who were later diagnosed with MCI and then Alzheimer's. The longitudinal brain scans of each group were compared in order to note CA1 and subicular atrophy.
In agreement with the first study, the subgroup that was later diagnosed with Alzheimer's presented the same pattern of atrophy spreading in the same regions of the hippocampus, wrote the authors.
In addition, atrophy that cascades across the entire hippocampus of the brain was noted as the pattern that Alzheimer's disease follows and excess atrophy found on the scans can be considered a biomarker for individuals who will later develop MCI, but have not presented any outward personality or cognitive changes yet, said Apostolova and colleagues.
The researchers also noted that very sensitive scanning techniques are required to observe the degree of atrophy, because progression is not easily visible on brain scan images.
"We can't see the pathologic changes, but we clearly see the neurodegenerative atrophy associated with MCI and Alzheimer’s, and how it spreads through the hippocampus," said Apostolova.