科研之友
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摘要
Molecular neuroimaging techniques such as PET are proving valuable in the early and differential diagnosis of Alzheimer's disease (AD). With the advent of new therapeutic strategies aimed at reducing beta-amyloid (A beta) burden in the brain to potentially prevent or delay functional and irreversible cognitive loss, there is increased interest in developing agents that allow assessment of A beta burden in vivo.
Amyloid imaging with PET has proven useful in the discrimination of dementias, showing significantly higher A beta burden in the gray matter of AD patients when compared with healthy controls or patients with frontotemporal dementia. ApoE epsilon 4 carriers, independent of diagnosis or disease severity, present with higher A beta burden than non-epsilon 4 carriers. Amyloid imaging matches histopathological reports in aging and dementia, reflecting the true regional density of A beta plaques in cortical areas. It also appears to be more sensitive than FDG-PET for the diagnosis of AD.
In healthy older people there is an increasing prevalence of amyloid positive scans with age, rising from 20% in the seventh decade to 60% in the ninth decade. Of people with mild cognitive impairment (MCI), 40-60% present with detectable cortical A beta deposition. In both groups, PO deposition is associated with a higher risk for cognitive decline and dementia due to AD. These observations suggest that A beta deposition is not part of normal aging, supporting the hypothesis that it occurs well before the onset of symptoms and is likely to represent preclinical AD in asymptomatic persons and prodromal AD in MCI. Further longitudinal observations, coupled with different disease-specific tracers and biomarkers, are required to confirm this hypothesis and further elucidate the precise role of A beta deposition in the course of AD.
- 出版日期2011-9
