A team of University of California, Los Angeles (UCLA) scientists who developed a chemical marker to help assess the neurological changes associated with cognitive impairment and dementia have found the brain-imaging tool effectively tracked and predicted cognitive decline over a two-year period, according to a study published in the February issue of Archives of Neurology.

The marker [18F]FDDNP binds to both plaque and tangle deposits, which can then be viewed using a PET scan. Using this method, researchers are able to pinpoint where the abnormal protein deposits are accumulating.

"We are finding this may be a useful neuroimaging marker that can detect changes early, before symptoms appear, and it may be helpful in tracking changes in the brain over time," Gary W. Small, MD, UCLA's Parlow–Solomon Professor on Aging and a professor of psychiatry at the Semel Institute for Neuroscience and Human Behavior at UCLA, said in a statement.

To determine whether [18F]FDDNP brain regional values in individuals without dementia predicted future cognitive change, the researchers performed brain scans on a volunteer sample of 43 middle-aged and older participants. Approximately half (21), had mild cognitive impairment (MCI), while the rest had normal aging. Scans and cognitive assessments on the subjects were performed at baseline and then again two years later.

Results showed that for both the MCI and normal aging groups, increases in frontal, posterior cingulate and global [18F]FDDNP binding at follow-up correlated with progression of memory decline. Higher baseline [18F]FDDNP binding was associated with decline in other areas such as language, attention, executive and visuospatial abilities.

Among the MCI group, the greatest diagnostic accuracy in identifying converters to Alzheimer’s disease was seen in frontal and parietal [18F]FDDNP binding. Six of the MCI subjects were diagnosed with Alzheimer’s at the two-year follow-up and these subjects had higher initial frontal and parietal binding values than the other subjects in their group.

“The finding that MCI patients with high frontal and parietal binding are more likely to convert to Alzheimer's disease after two years than those with low binding in these regions further supports the potential utility of [18F]FDDNP PET as a biomarker predictor of cognitive decline in MCI,” wrote the authors.

In the normal aging subjects, three developed mild cognitive impairment after two years. Two of these three participants had had the highest baseline binding values in the temporal, parietal and frontal brain regions among this group.

“We expect that many of the normal aging individuals in this study will eventually progress to MCI, and those with higher baseline[18F]FDDNP binding, particularly in the medial temporal region, might be at the greatest risk for decline within the next few years,” wrote the authors.

The next step, according to the researchers, will be research involving longer duration of follow-up with larger samples of subjects.

"Because FDDNP appears to predict who will develop dementia, it may be particularly useful in tracking the effectiveness of interventions designed to delay the onset of dementia symptoms and eventually prevent the disease," said Small.