A PET scan (positron emission tomography) that measures uptake of sugar in the brain significantly improves the accuracy of diagnosing a type of dementia often mistaken for Alzheimer's disease, a study led by a University of Utah dementia expert has found.
The scan, FDG-PET, helped six doctors from three national Alzheimer's disease centers correctly diagnose frontotemporal dementia (FTD) and Alzheimer's in almost 90 percent of cases in the study—an improvement of as much as 14 percent from usual clinical diagnostic methods. FDG stands for fluorodeoxyglucose, a short-lived radioactive form of sugar injected into people during PET scans to show activity levels in different parts of the brain. In Alzheimer's, low activity is mostly in the back part of the brain; in FTD, low activity is mostly in the front of the brain.
FDG-PET is an especially powerful tool in early treatment of FTD, said the study's lead author, Norman L. Foster, M.D., professor of neurology and director of the Center for Alzheimer's Care, Imaging and Research at the University of Utah School of Medicine.
FTD is a common cause of early onset dementia among people 45-64 years old and is marked by behavioral changes and language difficulties. Like Alzheimer's, it can take years to develop and, for now, is incurable. Although FTD is a separate disorder, it often meets clinical diagnostic criteria for Alzheimer's and often is misdiagnosed even by dementia experts.
“Early diagnosis of FTD can have a tremendous impact on the treatment for patients and their family members. Many patients are misdiagnosed and may be hospitalized and receive drugs for the wrong disease,” Foster said. “Accurate diagnosis bypasses the costs, side-effects, and frustration of misguided care. Furthermore, one-third of FTD patients have a family history of a similar disorder and family members need to know if they are at increased risk of the disease.”
The study was funded by the National Institute on Aging, a part of the National Institutes of Health.
“Dr. Foster's work involving patients from several NIA-sponsored Alzheimer's Disease Centers advances the use of PET imaging as a clinical tool,” said Creighton Phelps, Ph.D., program director of the Alzheimer Disease Centers at the National Institute on Aging. “Combined with the patient's medical history and psychometric testing, it enhances a physician's ability to more accurately distinguish between FTD and early-onset AD.”
As the U.S. population ages, the number of people with dementia is projected to increase markedly, with Utah and the Intermountain West expected to experience the fastest rate of growth. Although FDG-PET is widely available, it is not often used in dementia, because of insurance concerns. Medicare recently agreed to pay for FDG-PET scans to evaluate dementia, but currently many insurance companies in the Intermountain West and Utah do not. Foster is working to make FDG-PET scans available to those who need them and results of this study prove they sometimes are worth doing.