In the past, physicians were able only to follow the progression of Alzheimer's disease (AD) through careful clinical histories, noting the often subtle changes associated with cognitive decline over a number of years.
Some studies have suggested that the characteristic signs of AD are present up to a decade before dementia sets in. The difficulty was being able to look into a living person's brain to see the deposits of plaque (an abnormal accumulation of insoluble fibrous beta-amyloid protein aggregates) thought to be responsible for the onset of the disease.
Using positron emission tomography (PET) and a radiotracer known as Pittsburgh Compound-B (PiB) that is capable of binding to plaques found in the brains of AD patients, researchers at the University of Pittsburgh found that beta-amyloid imaging could provide early detection of AD and more accurate differential diagnosis of other dementias (by revealing the presence or absence of beta-amyloid plaques).
In a current longitudinal study following participants for more than four years, the Pittsburgh research team has recently sought to compare patients with AD to elderly control individuals and to subjects with mild cognitive impairment (MCI) to determine control subjects at risk of developing cognitive impairment and those MCI subjects who were most likely to progress on to a clinical diagnosis of AD.
"The research literature shows that 30 to 40 percent of people with MCI do not progress to AD during five to 10 years of follow-up testing. Our hypothesis was that MCI subjects with brain plaque would develop AD and MCI subjects without plaque would not advance to AD," said Chester Mathis, Ph.D., professor of radiology at the University of Pittsburgh.
"We had also assumed that the elderly control group would have little PiB retention (indicating no amyloid deposits), but the results were otherwise," he added.
Dementia is a general term for a progressive brain dysfunction that results in the loss of memory and other intellectual abilities serious enough to interfere with daily life. MCI patients demonstrate a decline of cognitive performance that is more pronounced than expected from age but not severe enough to meet criteria for the clinical diagnosis of dementia.
