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PET Projects Alzheimer's

Brain scan accurately finds patients headed for serious dementia

TUESDAY, Nov. 6, 2001 (HealthDayNews) -- A test that measures the buzz of sugar in the brain can predict which nerve-disease patients are likely to have a serious mental decline, a new study confirms.

Researchers in the United States and Europe say positron emission tomography (PET) accurately detected brain changes that lead to the dementia of Alzheimer's and other such degenerative diseases in at least 90 percent of patients they studied. The imaging tool works even better to identify the earliest stages of dementia in Alzheimer's, finding these signals 95 percent of the time.

"We found that PET opens a window into the living brain with a degree of accuracy matched only by autopsy," said lead study author Dr. Dan Silverman, a pharmacologist at the University of California at Los Angeles, in a statement today. "Physicians can perform this procedure non-invasively on living patients and detect dementia early enough for clinical intervention." A PET scan measures the flow of blood sugar -- the fuel for the brain -- as it is used by the organ.

The Food and Drug Administration has approved drugs to treat Alzheimer's dementia, but the medications usually can delay hospitalization for the condition by only about six months or so.

Dr. Edward Coleman, a Duke University radiologist, says PET scans will let doctors diagnose Alzheimer's earlier and therefore may make therapies for dementia more effective. "I think it's going to make a major impact in the way we are going to take care of these patients," says Coleman.

The findings will appear this week in the Journal of the American Medical Association.

Earlier research has shown that PET scans can ferret out signs of Alzheimer's disease that otherwise might go undetected for years. The non-invasive technology uses a radioactive tracer injected into the body to monitor the activity of brain cells -- neurons -- and report vivid pictures of the organ.

Even budding Alzheimer's disease leaves a fingerprint in the form of muted use of blood sugar by tissue in the brain's temporoparietal lobes, a center involved the complex processing of memory, thought and mental agility. Other neurodegenerative disorders, such as non-Alzheimer's dementia, also have standout scans.

The latest study followed 284 men and women with varying stages of dementia for two to nine years. One group of 146 patients were given PET scans and then watched for signs of continued cognitive decline. The remaining 138 had autopsies after they died to identify Alzheimer's disease or similar dementia disorders.

Abnormal PET scans successfully predicted worsening dementia in 191 of 210 patients, or 91 percent. Those whose scans were normal, on the other hand, had only a 10 percent chance of experiencing continued mental decline over an average of three years of follow-up.

"PET's ability to diagnose dementia in its earliest stage holds great significance because medical management offers the most benefit during the initial period of decline," says Silverman.

Study co-author Mony J. de Leon, an experimental psychiatrist at New York University School of Medicine, says this and other work strongly suggests that PET will be useful to doctors hoping to identify people with budding dementia disorders.

PET also appears to be able to detect extremely early evidence of pre-clinical brain trouble that likely will progress to Alzheimer's, says de Leon, who recently published a study on the issue. And he says he's almost ready to recommend that healthy people with a family history of Alzheimer's or other strong risk factor for the disease consider getting the scans. "But it has to be couched with the proviso that the overall accuracy of the technology needs to be better learned," de Leon says.

What To Do

About 4 million Americans now suffer from Alzheimer's disease, says the Alzheimer's Association. As the population ages, that number is expected to surge to 14 million by the year 2050, the group says.

For more on the disease, which has no cure, try the Alzheimer's Association or the Centers for Disease Control and Prevention.

To learn more about PET scans, check Guy's and St. Thomas' Hospitals or sign up for a free Alzheimer's caregiver's kit from the National Family Caregivers Association.

SOURCES: Interviews with Edward Coleman, M.D., professor of radiology, Duke University Medical Center, Durham, N.C.; Mony de Leon, Ed.D., professor of experimental psychiatry, New York University School of Medicine, New York City; Nov. 7, 2001, Journal of the American Medical Association
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