In the study, brain scans of adults with Down syndrome showed increased metabolic activity in the temporal cortex the same region of the brain where Alzheimer's disease commonly develops. The researchers speculate that Alzheimer's may begin with a similar metabolic increase, because Down syndrome often leads to dementia during adulthood
If so, a common PET scan procedure could allow early detection of Alzheimer's.
Study results appear in the Dec. 23 issue of Neurology.
According to Richard Haier, professor of pediatrics and principal investigator of the study, neurons work efficiently in normal brains, but in diseased brains, damaged neurons have to work harder to maintain their effectiveness, as revealed by the metabolic rate increases in Down syndrome brains. This damage most likely comes from the progressive accumulation of both senile plaques and neurofibrillary tangles, the two lesions associated with both Down syndrome and Alzheimer's. When the damaged neurons are ultimately destroyed by these lesions, the metabolic rate will decrease, as was observed in the Alzheimer's-diseased brains scanned for the study.
"These findings suggest that Down syndrome dementia and possibly Alzheimer's disease may begin when neuronal damage in the temporal cortex region reaches the point where increased metabolism can no longer compensate," Haier said. "But to confirm this, further imaging tests must be done on the Down syndrome people as dementia progresses."
Nearly 350,000 Americans have Down syndrome, which is a genetic disorder caused by the inheritance of three copies of the 21st chromosome. People with Down syndrome show some of the brain changes of Alzheimer's as early as age 12. Nearly all Down synd
Contact: Tom Vasich
University of California - Irvine