Figure Legend: A side-by-side comparison of baseline EEG
traces of the frontal regions of the brain in two
individuals. On the left is the EEG of a normal elderly
individual who does not decline cognitively. On the right is
the EEG of an individual who will decline over the next 7
years. The slower, deeper waves on the right show abnormal
theta activity, a sign of eventual dementia. The color-coded
images on top of the EEGs depict the theta activity. The
blue shows normal activity and the yellow shows significant
excess of theta.
Although Alzheimer’s disease
affects millions of people worldwide, there is no way to identify
this devastating brain disease at its earliest stages when there
still may be time to delay or even prevent the downward spiral into
dementia.
In research settings, scientists
are using sophisticated tools like MRI and PET to distinguish
characteristics of brain function and anatomy that indicate future
problems, providing a sort of screening test for the brain.
Now a new study by a research
group at NYU School of Medicine demonstrates that the earliest
manifestations of Alzheimer’s, when the first signs of memory loss
appear, can be screened with a relatively inexpensive, painless, and
easy-to-use tool called an EEG (electroencephalograph). (See
attached graphic)
In the study, published in the
upcoming on line issue of the journal Neurobiology of Aging,
the researchers demonstrate that a computer analysis of the EEG,
which measures the brain’s electrical activity, accurately predicted
healthy people in their 60s and 70s who would develop dementia over
the next 7 to 10 years. It also identified individuals who would
remain virtually unchanged over the same time span. The EEGs were
almost 95 percent accurate in identifying those who would decline
cognitively and those who would not, according to the study.
“Our results suggest that
quantitative analysis of the EEG is sensitive to the earliest signs
of the dementing process,” says Leslie S. Prichep, Ph.D., Associate
Director of the Brain Research Laboratories of the Department of
Psychiatry, who led the study. Some day she says it may be used as
one of the tools to evaluate a person’s propensity for developing
Alzheimer’s, the most common form of dementia affecting people over
65. But for now the results need to be replicated in and validated
by much larger prospective studies before they can be applied to
screen large populations.
It takes about 30 minutes to
perform an EEG, which involves placing recording electrodes on the
scalp. The test is perfomed with the patient seated comfortably.
There are no injections and the scalp is not shaved.
The NYU researchers, led by Dr.
Prichep and Roy John, Ph.D., Professor in the Department of
Psychiatry, evaluated a group of 44 individuals between the ages of
64 and 79 who felt that their memories were faltering. These people
enrolled voluntarily in a long-term study at NYU’s Silberstein Aging
and Dementia Research Center where they underwent a battery of
neuropsychiatric and other tests, which revealed that their brain
function was normal for their age.
At the beginning of the testing
process each volunteer was also given a baseline EEG test at the
Brain Research Laboratories at NYU School of Medicine. They were
tested there several more times over the next 7 to 10 years. Over
this period, 27 of the 44 subjects developed mild cognitive
impairment or full-blown dementia, and 17 remained stable. Applying
a mathematical algorhythm to the brain scans, Drs. Prichep and John
showed that certain characteristics of the pattern of brain waves on
the baseline EEG were associated with future cognitive
deterioration.
To the untrained eye EEGs look
like a confusing thicket of squiggly lines. But the lines are
actually waves that have been described mathematically by their
amplitude and frequency composition as a function of age, based on
data collected over the last 30 years by Drs. Prichep and John. They
and their NYU colleagues obtained this data from some 12,000 healthy
people and psychiatric patients who had been given EEGs. About 3,500
of the EEGs were from aging and dementia patients.
“We probably have the largest
electrophysiological database of this kind in the world,” says Dr.
Prichep. “Since we can compare each individual’s quantitative EEG to
age-expected normal values, we were able to describe which features
reflected expected changes occurring with normal aging and which
might be associated with future decline,” she says.
A prominent feature associated
with cognitive deterioration on the baseline EEG was a brain wave
called theta, which was excessive in people who would eventually
decline, according to the study. This band was particularly abnormal
in the frontal regions, along the lateral regions and in the right
posterior region of the brain in those people who went on to
decline.
Another feature was a slowing in
the mean frequency of the EEG, which is described in cycles per
second. Yet another distinctive feature of those who decline was a
change in the synchronization between the two sides of the brain.
The source of the theta has been shown to be the hippocampus, a
brain region demonstrated in imaging studies with MRI and PET to be
impaired in dementia, notes Dr. Prichep.
The NYU researchers who
contributed to this study are Drs. Prichep and John, 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.
