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New Imaging Captures Alzheimer's Onset

Technique uses chemical tracing to reveal early signs of degenerative condition

WEDNESDAY, Jan. 9, 2002 (HealthDayNews) -- Scientists say they have developed the first imaging technique that detects the early signs of brain damage from Alzheimer's disease.

The procedure is the first that could be used to track the progression of the disease in living patients, and researchers hope it leads to better diagnosis and therapies for people who are struck by the crippling condition.

The technique is described in the January issue of the American Journal of Geriatric Psychiatry.

Alzheimer's disease is a degenerative brain condition that causes progressive memory loss, and eventually dementia. While the cause of the disease is not known, scientists believe it involves the formation of abnormal clumps, called amyloid plaques, and tangled bundles of fibers, known as neurofibrillary tangles, in the brain.

While several drugs can relieve some of the disease's symptoms, there is no known cure. About 4 million Americans suffer from Alzheimer's disease, a figure that is expected to jump to 14 million by 2050.

"It's a devastating disease," says lead author Jorge R. Barrio, a professor of medical and molecular pharmacology at the University of California, Los Angeles.

Currently, the only definitive diagnosis for Alzheimer's disease is autopsy evidence from the patient's brain. Diagnosis usually occurs only after the symptoms of the disease develop, meaning that significant brain damage has already occurred.

In the study, Barrio and his colleagues injected a chemical called FDDNP into nine patients who had probable or possible Alzheimer's disease and seven healthy volunteers. They then scanned their brains, using positron emission tomography (PET), for about one hour.

The FDDNP acts as a chemical tracer, binding to the plaques and tangles, explains Barrio.

They found that in the Alzheimer's patients, the FDDNP accumulated in high concentrations in areas of the brain responsible for memory. On the PET images, the tracer lit up regions of the brain where it was most active, revealing early lesions.

When one of the nine patients with Alzheimer's disease died, the researchers performed a brain autopsy. They found brain lesions stained with FDDNP in the patient's right hemisphere, which further confirmed the findings of the study.

"If one could identify patients very early – as early as possible, even before the symptoms appear – then you have a much better chance for therapeutic intervention," says Barrio.

He points out that such a test could also rule out other forms of dementia that are currently indistinguishable from Alzheimer's until an autopsy is performed.

Bill Thies, the vice president of medical and scientific affairs for the Alzheimer's Association, says that researchers have been aiming for the ability to image Alzheimer's in living patients for years. "It is significant that they've been able to do it in humans," he says.

"As we begin to look for medications that can prevent progression of the disease, it makes great sense to have a technique that will identify the disease before it becomes symptomatic," says Thies. "Obviously, if we can prevent it before symptoms occur, the disease never happens."

"This kind of approach, of trying to look for an early indicator of Alzheimer's disease, is going to be a key part of that," he adds. However, he cautions that this is a very small study and that it's not yet clear whether the final version of this test will use this specific chemical tracer.

The researchers are looking at several other chemical markers that Barrio says may be even more promising than FDDNP.

Barrio hopes to receive approval from the U.S. Food and Drug Administration for further clinical trials of this technique, which he says could be available for widespread use in several years.

What To Do

For more information on Alzheimer's disease, visit the Alzheimer's Association or the National Institute on Aging's Alzheimer's Disease Education and Referral Center.

To find out more about PET technology, check out the University of California, Los Angeles.

SOURCES: Interview with Jorge R. Barrio, Ph.D., professor, Division of Nuclear Medicine, Department of Molecular and Medical Pharmacology, University of California, Los Angeles School of Medicine, Los Angeles; Bill Thies, Ph.D., vice president of medical and scientific affairs, Alzheimer's Association, Chicago; January 2002 American Journal of Geriatric Psychiatry
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