Objective: The aim of the study was to examine vulnerable brain areas , such as the hippocampus and cingulate gyrus, in subjects with Mild Cognitive Impairment (MCI) , Mild Probable Alzheimer's Disease ( MPRAD) and normal, healthy, age, sex and education matched controls with Proton Nuclear Magnetic Resonance Spectroscopy ( 1H-NMRS).
Design: This is a cross-sectional study comparing three groups of subjects: MCI, MPRAD and Control. All subjects were scanned once at the University of Chicago, Dept of Radiology, with the identical protocol by the PI, and three brain areas were identified for the study: right and left hippocampus and posterior cingulate gyrus. Data from the scans were collected at the time of the study and analyzed by student's t test or repeated measures analysis of variance.
Materials and Methods: All subjects were recruited from the University of Chicago Memory Center or the Northwestern Alzheimer's Disease Center and were diagnosed by consensus after extensive neuropsychological testing and neurological exam. All NMRS scans were performed on a 3T GE whole body system with appropriate head coil. The scans took approximately 45 minutes. We acquired single voxel proton data in three areas of interest (ROI): right hippocampus, left hippocampus and posterior cingulate gyrus after obtaining a structural MRI. ROI's were determined by visual placement and voxel size was 2x2x1 cm. MRS data is expressed as ratios of NAA( N-acetyl aspartate, CHO,(choline) and MI (myoinositol) to CR (creatine). We studied 8 MCI, 6 MPRAD and 17 Control Subjects.
Results: Mean MMSE for the three groups was 29.2 for Control, 28.5 for MCI and 22.8 for MPRAD. There were no significant differences between groups for age, sex or education. Mean MMSE of the MPRAD group was significantly different from Control and MCI groups, but the latter two did not differ from each other. We found a significant decrease( p<.003) of NAA/CR in the right hippocampus in MCI and MPRAD compared to Controls. Left hippocampal NAA/CR was also decreased in MCI and MPRAD compared to Controls but was not as significant. CHO/CR ratios and MI/CR ratios demonstrate no significant diffferences between groups in any brain area.
Conclusion: Since NAA is considered a marker of neuronal loss/integrity, our findings suggest that the right hippocampus may be affected quite early in the AD disease process, at the MCI stage, and needs to be evaluated along with the left hippocampus in future NMRS studies of AD and MCI. 1H-NMRS of bilateral hippocampi may be a useful adjunct to structural MRI in the diagnostic work-up of patients with mild cognitive impairments.
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