Although Alzheimer's disease affects millions of people worldwide,there is no way to identify this devastating brain disease at itsearliest stages when there still may be time to delay or even preventthe downward spiral into dementia. In research settings, scientists areusing sophisticated tools like MRI and PET to distinguishcharacteristics of brain function and anatomy that indicate futureproblems, providing a sort of screening test for the brain.
Now a new study by a research group at NYU School of Medicinedemonstrates that the earliest manifestations of Alzheimer's, when thefirst signs of memory loss appear, can be screened with a relativelyinexpensive, painless, and easy-to-use tool called an EEG(electroencephalograph).
In the study, published in the upcoming on-line issue of the journalNeurobiology of Aging, the researchers demonstrate that a computeranalysis of the EEG, which measures the brain's electrical activity,accurately predicted healthy people in their 60s and 70s who woulddevelop dementia over the next 7 to 10 years. It also identifiedindividuals who would remain virtually unchanged over the same timespan. The EEGs were almost 95 percent accurate in identifying those whowould decline cognitively and those who would not, according to thestudy.
"Our results suggest that quantitative analysis of the EEG is sensitiveto the earliest signs of the dementing process," says Leslie S.Prichep, Ph.D., Associate Director of the Brain Research Laboratoriesof the Department of Psychiatry, who led the study. Some day she saysit may be used as one of the tools to evaluate a person's propensityfor developing Alzheimer's, the most common form of dementia affectingpeople over 65. But for now the results need to be replicated in andvalidated by much larger prospective studies before they can be appliedto screen large populations.
It takes about 30 minutes to perform an EEG, which involves placingrecording electrodes on the scalp. The test is perfomed with thepatient seated comfortably. There are no injections and the scalp isnot shaved.
The NYU researchers, led by Dr. Prichep and Roy John, Ph.D.,Professor in the Department of Psychiatry, evaluated a group of 44individuals between the ages of 64 and 79 who felt that their memorieswere faltering. These people enrolled voluntarily in a long-term studyat NYU's Silberstein Aging and Dementia Research Center where theyunderwent a battery of neuropsychiatric and other tests, which revealedthat their brain function was normal for their age.
At the beginning of the testing process each volunteer was also given abaseline EEG test at the Brain Research Laboratories at NYU School ofMedicine. They were tested there several more times over the next 7 to10 years. Over this period, 27 of the 44 subjects developed mildcognitive impairment or full-blown dementia, and 17 remained stable.Applying a mathematical algorhythm to the brain scans, Drs. Prichep andJohn showed that certain characteristics of the pattern of brain waveson the baseline EEG were associated with future cognitivedeterioration.
To the untrained eye EEGs look like a confusing thicket of squigglylines. But the lines are actually waves that have been describedmathematically by their amplitude and frequency composition as afunction of age, based on data collected over the last 30 years by Drs.Prichep and John. They and their NYU colleagues obtained this data fromsome 12,000 healthy people and psychiatric patients who had been givenEEGs. About 3,500 of the EEGs were from aging and dementia patients.
"We probably have the largest electrophysiological database of thiskind in the world," says Dr. Prichep. "Since we can compare eachindividual's quantitative EEG to age-expected normal values, we wereable to describe which features reflected expected changes occurringwith normal aging and which might be associated with future decline,"she says.
A prominent feature associated with cognitive deterioration on thebaseline EEG was a brain wave called theta, which was excessive inpeople who would eventually decline, according to the study. This bandwas particularly abnormal in the frontal regions, along the lateralregions and in the right posterior region of the brain in those peoplewho went on to decline.
Another feature was a slowing in the mean frequency of the EEG, whichis described in cycles per second. Yet another distinctive feature ofthose who decline was a change in the synchronization between the twosides of the brain. The source of the theta has been shown to be thehippocampus, a brain region demonstrated in imaging studies with MRIand PET to be impaired in dementia, notes Dr. Prichep.
The NYU researchers who contributed to this study are Drs. Prichep andJohn, Steven Ferris, Ph.D., Lawrence Rausch, PhD, Zeke Fang, PhD,Robert Cancro, M.D., Carol Torossian, Ph.D. and Barry Reisberg, M.D.
The study was supported by grants from National Institutes of Health, among other organizations.
Materials provided by New York University Medical Center and School of Medicine. Note: Content may be edited for style and length.
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