Scans Show Alzheimer's Cruel March Through Brain
Cascade of withering begins with memory part before moving on
WEDNESDAY, April 3, 2002 (HealthDayNews) -- Scientists have known for more than two decades that the loss of function in Alzheimer's disease is caused by a steady deterioration of different parts of the brain. Now neurologists in England have painted a step-by-step picture of how and where that damage begins and spreads.
It's the memory part of the brain that goes first in this mind-robbing illness, the researchers report. Then the damage spreads to the regions involved in speech, perception and other functions. In the final stages of the disease, the region of the brain concerned with memory can shrink by two-thirds.
The researchers accomplished their feat by using three-dimensional magnetic resonance imaging (MRI) technology with three groups of people: some in the earliest stage of Alzheimer's before symptoms appear (people from families where the disease is endemic); some who were only moderately affected; and some in the last stages of the disease.
The study, done by researchers at the Institute of Neurology and the Imperial College of Science, Engineering and Medicine in London, "takes the story into a new chapter to show how the disease progresses, revealed by regional atrophy, spreads in a highly specific way from the medial temporal lobe to other parts of the brain," says a commentary accompanying the report in today's issue of the Proceedings of the National Academy of Sciences.
It's a study that someday could be used to help treat Alzheimer's, says Dr. Donald L. Price, professor of neurology, pathology and neuroscience at the Johns Hopkins School of Medicine. Treatments for this once unstoppable condition are starting to emerge, he notes.
"If a therapy has some downside, you want to be sure you are treating only Alzheimer's patients," Price says. "It would be critical to enhance the early diagnosis of Alzheimer's disease as differentiated from other forms of dementia."
Even before symptoms appear, the left hippocampus and right hippocampus, parts of the brain involved in verbal and nonverbal memory, begin to atrophy. Neurons -- nerve cells -- die. Connections wither, as tangles form in the regions that connect one part of the brain to others.
Memory starts to fail. As interconnections die, more nerve cells at the end of those connections show reduced activity. Tangles appear in those regions, and the cycle of loss of connections and loss of neurons spreads to other parts of the brain.
"We can imagine that an anatomically driven cascade process builds up," says the commentary by Dr. A. David Smith of Oxford University.
This picture "is not a therapeutic breakthrough," Price says. "There are several lines of evidence drawn from different technologies that show structural changes in parallel with evolution of the disease. But it is perhaps another weapon in the armamentarium of early diagnosis of Alzheimer's."
The Oxford report is part of a continuing effort in a number of medical centers to develop accurate ways to track the progression of Alzheimer's disease, says Bill Thies, vice president for medical and scientific affairs at the Alzheimer's Association.
"All the techniques are out there trying to see which is best," Thies says. "This report now goes out to other imaging folks to analyze and see whether it is worth trying on a large scale."
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The technology used in the study could be useful in medical practice, the researchers say: "The combination of the techniques that we describe may provide insights into disease progression in Alzheimer's disease and related disorders, and may be useful for tracking progression in clinical trials of new therapies."