Glucose metabolism, gray matter structure, and memory decline in subjective memory impairment.
OBJECTIVE
To identify biological evidence for Alzheimer disease (AD) in individuals with subjective memory impairment (SMI) and unimpaired cognitive performance and to investigate the longitudinal cognitive course in these subjects.


METHODS
[¹⁸F]fluoro-2-deoxyglucose PET (FDG-PET) and structural MRI were acquired in 31 subjects with SMI and 56 controls. Cognitive follow-up testing was performed (average follow-up time: 35 months). Differences in baseline brain imaging data and in memory decline were assessed between both groups. Associations of memory decline with brain imaging data were tested.


RESULTS
The SMI group showed hypometabolism in the right precuneus and hypermetabolism in the right medial temporal lobe. Gray matter volume was reduced in the right hippocampus in the SMI group. At follow-up, subjects with SMI showed a poorer performance than controls on measures of episodic memory. Longitudinal memory decline in the SMI group was associated with reduced glucose metabolism in the right precuneus at baseline.


CONCLUSIONS
The cross-sectional difference in 2 independent neuroimaging modalities indicates early AD pathology in SMI. The poorer memory performance at follow-up and the association of reduced longitudinal memory performance with hypometabolism in the precuneus at baseline support the concept of SMI as the earliest manifestation of AD.
Department of Radiology, University of Bonn, Bonn, Germany.
Lukas
L
Scheef
Annika
A
Spottke
Moritz
M
Daerr
Alexius
A
Joe
Nadine
N
Striepens
Heike
H
Kölsch
Julius
J
Popp
Marcel
M
Daamen
Dominik
D
Gorris
Michael T
MT
Heneka
Henning
H
Boecker
Hans J
HJ
Biersack
Wolfgang
W
Maier
Hans H
HH
Schild
Michael
M
Wagner
Frank
F
Jessen
D000368:Aged; D001921:Brain / Q000378:metabolism / Q000473:pathology / Q000503:physiopathology*; D005260:Female; D019788:Fluorodeoxyglucose F18; D005500:Follow-Up Studies; D005947:Glucose / Q000378:metabolism*; D006801:Humans; D008279:Magnetic Resonance Imaging / Q000379:methods*; D008297:Male; D008569:Memory Disorders / Q000175:diagnosis*; D061212:Memory, Episodic; D009483:Neuropsychological Tests; D049268:Positron-Emission Tomography / Q000379:methods*
D019788:Fluorodeoxyglucose F18; D005947:Glucose