Temporal cortex hypermetabolism in Down syndrome prior to the onset of dementia.
BACKGROUND
Adults with Down syndrome (DS) are at increased risk for dementia and provide an opportunity to identify patterns of brain activity that may precede dementia. Studies of early Alzheimer's disease (AD) and risk of AD show decreased function in posterior cingulate and temporal cortex as initial indicators of the disease process, but whether the origin and sequence of predementia brain changes are the same in DS is unknown.


METHODS
The regional cerebral glucose metabolic rates (GMR) among middle-aged nondemented people with DS (n = 17), people with moderate AD (n = 10), and age-matched control subjects (n = 24) were compared using PET during a cognitive task.


RESULTS
Statistical parametric mapping conjunction analyses showed that 1) both DS and AD groups had lower GMR than their respective controls primarily in posterior cingulate and 2) compared with respective controls, the subjects with DS had higher GMR in the same areas of inferior temporal/entorhinal cortex where the AD subjects had lower GMR. The same results were replicated after 1 year of follow-up.


CONCLUSIONS
As the DS subjects were not clinically demented, inferior temporal/entorhinal cortex hypermetabolism may reflect a compensatory response early in disease progression. Compensatory responses may subsequently fail, leading to neurodegenerative processes that the authors anticipate will be detectable in vivo as future GMR decreases in inferior temporal/entorhinal cortex are accompanied by clinical signs of dementia.
Haier
R J
RJ
Department of Pediatrics, University of California, Irvine 92697-5000, USA. rjhaier@uci.edu
Alkire
M T
MT
White
N S
NS
Uncapher
M R
MR
Head
E
E
Lott
I T
IT
Cotman
C W
CW
D000328:Adult; D000368:Aged; D000544:Alzheimer Disease / Q000175:diagnosis / Q000000981:diagnostic imaging / Q000378:metabolism*; D004314:Down Syndrome / Q000175:diagnosis / Q000000981:diagnostic imaging / Q000378:metabolism*; D018728:Entorhinal Cortex / Q000000981:diagnostic imaging / Q000378:metabolism; D005260:Female; D019788:Fluorodeoxyglucose F18 / Q000493:pharmacokinetics; D005500:Follow-Up Studies; D005947:Glucose / Q000378:metabolism*; D006179:Gyrus Cinguli / Q000000981:diagnostic imaging / Q000378:metabolism; D006801:Humans; D008297:Male; D008875:Middle Aged; D009483:Neuropsychological Tests; D012016:Reference Values; D015203:Reproducibility of Results; D013702:Temporal Lobe / Q000000981:diagnostic imaging / Q000378:metabolism*; D014055:Tomography, Emission-Computed
D019788:Fluorodeoxyglucose F18; D005947:Glucose