Mapping brain morphological and functional conversion patterns in amnestic MCI: a voxel-based MRI and FDG-PET study.
OBJECTIVE
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.


CONCLUSIONS
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.
Morbelli
Silvia
S
Nuclear Medicine Unit, Department of Internal Medicine, University of Genoa, Viale Benedetto XV, 6, 16132 Genoa, Italy. silviadaniela.morbelli@hsanmartino.it
Piccardo
Arnoldo
A
Villavecchia
Giampiero
G
Dessi
Barbara
B
Brugnolo
Andrea
A
Piccini
Alessandra
A
Caroli
Anna
A
Frisoni
Giovanni
G
Rodriguez
Guido
G
Nobili
Flavio
F
D000368:Aged; D000369:Aged, 80 and over; D000647:Amnesia / Q000150:complications* / Q000175:diagnosis*; D001921:Brain / Q000473:pathology*; D001931:Brain Mapping / Q000379:methods; D003072:Cognition Disorders / Q000150:complications* / Q000175:diagnosis*; D005260:Female; D019788:Fluorodeoxyglucose F18; D006801:Humans; D008279:Magnetic Resonance Imaging / Q000379:methods*; D008297:Male; D008875:Middle Aged; D049268:Positron-Emission Tomography / Q000379:methods*; D019275:Radiopharmaceuticals; D015203:Reproducibility of Results; D012680:Sensitivity and Specificity; D013382:Subtraction Technique
D019275:Radiopharmaceuticals; D019788:Fluorodeoxyglucose F18