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Better Scanning for Alzheimer Patients
By Melinda T. Willis
ABCNews.com, January 10, 2002
New imaging technique may make it possible to view brain lesions in
living patients in order to diagnose and treat Alzheimer's disease at an earlier stage
An imaging study conducted by UCLA researchers and published in the American Journal of Geriatric Psychiatry is the first of its kind to show the plaques and tangles that are characteristic of Alzheimer's in the brains of living patients. Prior to this study, viewing these brain lesions was only possible through examination after the patient had died.
The researchers involved in the imaging study injected a protein with a radioactive tracer into nine Alzheimer's patients. The protein, known as FDDNP, bound to the plaques and tangles in the brains of these patients. A PET scan, or positron emission tomography, was then used to image the location of these lesions in the brain.
"I think it's an important finding insofar as it's the first demonstration of the ability to image the pathology in the brain of patients with Alzheimer's disease," says Dr. Ronald Petersen, director of the Alzheimer's Disease Research Center at the Mayo Clinic in Rochester, Minn.
A Step in the Right Direction
Experts say that imaging techniques like PET scans have thus far only been able to show the result of disease progression, such as shrinkage or atrophy of the brain.
"People have been trying to measure [the plaques and tangles] because even if they don't cause Alzheimer's, they are the best marker for disease progression [in the brain]," says Dr. Gary Small, Parlow-Solomon professor of aging and UCLA professor of psychiatry and biobehavioral sciences and co-author of the paper.
"Now what this study is demonstrating is that we perhaps can actually see the causative process of the shrinkage," says Petersen.
However, experts say the imaging technique is not truly diagnostic. While plaques and tangles are hallmarks of Alzheimer's, these brain lesions are also found during autopsies of people who did not have the disease, so there is not a 1-to-1 correlation between the appearance of plaques and tangles and the development of Alzheimer's.
"They may be getting it in another five to 10 years — we just don't know that yet," says Dr. Steven DeKosky, director of the Alzheimer's Disease Research Center at the University of Pittsburgh.
Clinical Implications
Experts say that this new imaging technique has important immediate implications for the development of new drugs.
"This discovery will move that drug discovery forward a lot quicker, because where the field of Alzheimer's is going is getting rid of the plaques and tangles," says Small.
And PET scans could aid researchers when it comes to determining the efficacy of new medications.
"We're going to need a way to see whether or not the drugs are working rather than wait to see if the patient develops the disease," says DeKosky. "So these kinds of strategies for using PET to visualize the amount of [plaque] in the brain in the living person harmlessly is one of the major things we'd like to achieve within the next two to three years."
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