A unique brain scanner is used to allow the assessment of amyloid plaques and neurofibrillary tangles- the hallmarks of Alzheimer's disease- in adults with Down syndrome. This finding may offer a new clinical tool to help diagnose dementia in adults with Down syndrome.
Adults with this disorder develop Alzheimer's-like plaque and tangle deposits early, often before the age of 40. Previously, the only way to physically detect these abnormal proteins in this population was through an autopsy.
Over the last decade, methods for identifying and imaging the neuropathology of Alzheimer's disease in living patients have been developed. UCLA researchers have created a chemical marker called FDDNP that binds to both plaque and tangle deposits, which can then be viewed through a positron emission tomography (PET) brain scan, providing a "window into the brain." Using this method, researchers are able to pinpoint where in the brain these abnormal protein deposits are accumulating.
"Early detection can also lead to earlier interventions and treatments, often before symptoms begin."
For this study, researchers intravenously administered FDDNP and then performed PET brain scans on 19 non-demented adults with Down syndrome (average age 37), 10 healthy controls (average age 43) and 10 patients with Alzheimer's disease (average age 66).
The results showed significantly higher binding levels of FDDNP in participants with Down syndrome in all brain regions, when compared to healthy controls. Compared with Alzheimer's disease patients, subjects with Down syndrome showed significantly higher binding levels in the parietal and frontal regions — areas involved in memory, behavior and reasoning.
"The higher level of plaques and tangles may be reflecting the early and extensive accumulation of these deposits seen in individuals with Down syndrome," Dr. Small said.
The researchers also discovered significant associations between increased age in those with Down syndrome and higher FDDNP binding values in the parietal, lateral temporal and frontal regions.
"This is one of the first times we've been able to visualize the neuropathology occurring in the living brains of adults with Down syndrome," study author Dr. Jorge R. Barrio, a professor of molecular and medical pharmacology at the David Geffen School of Medicine at UCLA who holds UCLA's Plott Chair in Gerontology, was quoted as saying.
"The age-related patterns and regional distribution of the plaques and tangles were consistent with the types of deposits that could only be identified previously through an autopsy."
The areas of accumulation were consistent with earlier autopsy study findings, which had shown that while plaque and tangle pathologies are the same in both Down syndrome and Alzheimer's disease, the deposit patterns are different.
Autopsy studies have also shown that all adults with Down syndrome eventually develop these accumulations of amyloid plaques and tau tangles. But rather than experiencing memory decline and other cognitive losses, as is common with Alzheimer's, aging Down syndrome patients tend to develop behavioral problems.
"We found that the behavioral changes in the subjects with Down syndrome correlated with neurological changes in related areas of the brain consistent with the level of FDDNP binding levels to the abnormal proteins," Dr. Small said.