In spite of considerable research efforts which have been focused on exploring various aspects of Alzheimer's Disease (AD), much remains unknown about the disease including its etiology. One of the many puzzling issues observed in AD is the poor correlation between dementia and brain atrophy seen on CT scans. There are too many false positive (no dememtia with CT atrophy) and false negative (dementia and no CT atrophy) cases for this correlation to be of diagnostic value. However, CT scans are frequently performed on elderly individuals with suspected dementia as a procedure to rule out other conditions which might cause dementia such as mass lesions or infarctions. We postulate that predictive information for the course of dementia might be buried in these incongruent CT-and-dementia configurations. The rate of deterioration over time might be slower for the false negatives relative to the true positives (dementia and atrophy). The false positives, on the other hand, might deteriorate at a faster rate than the true negatives (no dementia and no atrophy). This information is of considerable clinical value in working with elderly individuals. Four groups of subjects (true positives, false negatives, false positives, and true negatives), one hundred in all, will be followed in a prospective, repeated measures paradigm. Magnetic Resonance Imaging (MRI), CT, and comprehensive neuropsychological evaluations will be administered at baseline and repeated 18 months later. This paradigm will provide information not only on how the two target groups of subjects (false positives and false negatives) evolve over time, but also provide longitudinal information on MIR, CT, and cognitive measures. There are indications that the newly available MRI might prove to be a more sensitive measure in representing brain abnormalities associated with dementia relative to CT scans. We propose to examine the validity of this preliminary indication.
