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Published on: June 26, 2013
Mapping brain morphological and functional conversion patterns in amnestic MCI: a voxel-based MRI and FDG-PET study
Silvia Morbelli1, Arnoldo Piccardo, Giampiero Villavecchia
1Nuclear Medicine Unit, Department of Internal Medicine, University of Genoa, Viale Benedetto XV, 6, 16132 Genoa, Italy. silviadaniela.morbelli@hsanmartino.it
Purpose:
To reveal the morphological and functional substrates of memory impairment and conversion to Alzheimer disease (AD) from the stage of amnestic mild cognitive impairment (aMCI).
Methods:
Brain MRI and FDG-PET were performed in 20 patients with aMCI and 12 controls at baseline. During a mean follow-up of about 2 years, 9 patients developed AD (converters), and 11 did not (nonconverters). All images were processed with SPM2. FDG-PET and segmented grey matter (GM) images were compared in: (1) converters versus controls, (2) nonconverters versus controls, and (3) converters versus nonconverters.
Results:
As compared to controls, converters showed lower GM density in the left parahippocampal gyrus and both thalami, and hypometabolism in the precuneus, posterior cingulate and superior parietal lobule in the left hemisphere. Hypometabolism was found in nonconverters as compared to controls in the left precuneus and posterior cingulated gyrus. As compared to nonconverters, converters showed significant hypometabolism in the left middle and superior temporal gyri.
Conclusion:
The discordant topography between atrophy and hypometabolism reported in AD is already present at the aMCI stage. Posterior cingulate-precuneus hypometabolism seemed to be an early sign of memory deficit, whereas hypometabolism in the left temporal cortex marked the conversion to AD.
Insights
Early Alzheimer disease (AD) detection in amnestic mild cognitive impairment (aMCI) shows distinct brain changes. Posterior cingulate-precuneus hypometabolism signals memory issues, while left temporal cortex changes predict conversion to AD.
Area of Science:
- Neuroimaging
- Neurology
- Alzheimer's Disease Research
Background:
- Amnestic mild cognitive impairment (aMCI) is a prodromal stage for Alzheimer disease (AD).
- Understanding the transition from aMCI to AD requires identifying early neurobiological markers.
Purpose of the Study:
- To investigate the morphological and functional brain changes associated with memory impairment in aMCI.
- To identify substrates predicting conversion from aMCI to Alzheimer disease.
Main Methods:
- Utilized brain MRI and FDG-PET in 20 aMCI patients and 12 controls.
- Tracked conversion to AD over a 2-year follow-up period.
- Compared grey matter density and glucose metabolism between converters, non-converters, and controls using SPM2.
Main Results:
- Converters showed reduced grey matter in the parahippocampal gyrus and thalami compared to controls.
- Hypometabolism was observed in the precuneus and posterior cingulate gyrus in both converters and non-converters versus controls.
- Converters exhibited greater hypometabolism in the left temporal cortex compared to non-converters.
Conclusions:
- Discrepancies between atrophy and hypometabolism, characteristic of AD, are evident at the aMCI stage.
- Posterior cingulate-precuneus hypometabolism may indicate early memory deficits.
- Left temporal cortex hypometabolism appears to be a marker for progression to Alzheimer disease.
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