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Scientists Discover Early Diagnosis Tool for Alzheimer's - 2002-01-31

There has been a major breakthrough in the diagnosis of Alzheimer's disease. For the first time, researchers say they are able to see lesions that are characteristic of Alzheimer's disease in a living human brain.

Alzheimer's disease is a common, but devastating, form of dementia that begins with memory loss and eventually leads to death.

Until now, the only way to learn for certain if patients suffer from Alzheimer's disease is to wait until they die, and then examine their brains for the tell tale protein plaques and tangles that are unique to Alzheimer's disease.

Gary Small, director of the Center on Aging at the University of California Los Angeles, says he believes there are a number of reasons to diagnose Alzheimer's disease at the earliest possible stages.

"We know that these plaques and tangles are correlating with the disease progression and are, in fact, accumulating not just years, but decades before the symptoms and signs are apparent to the family members," he said. "So, if we have a way to track these plaques and tangles, we have a way to track the disease early. And we have a way to start studying new treatments to clear them out of the brain."

Dr. Small co-authored a study, published in the American Journal of Geriatric Psychiatry, describing how researchers imaged the plaques and tangles of Alzheimer's patients.

Dr. Small says investigators faced a number of challenges. He says the researchers needed to find a molecule small enough to get past the body's natural mechanism for protecting the brain from foreign substances, known as the blood-brain barrier. The molecule also had to stick to Alzheimer's plaques and tangles.

"Inside the plaques and tangles it is what we call a hydrophobic, meaning that it does not like water," he said. "And these chemicals are attracted to those kinds of environments. So that is what we think is the piece of the puzzle that helped us address the challenge."

To actually see the plaques and tangles, the scientists exposed the chemical molecules placed into the brain to a harmless amount of radioactivity, causing them to glow. Investigators then took pictures of patients' brains using Positron Emission Tomography, a high-tech form of imaging known as PET.

Charles Smith is a professor of neurology at the University of Kentucky. Dr. Smith, whose research has involved using Magnetic Resonance Imaging to diagnose Alzheimer's disease, calls the strategy used by UCLA researchers unique and exciting.

"And what I think is special about it is rather than looking for blood flow changes and changes for metabolism of neurons in the brain, which has been done previously with PET, the investigators used a specific tag that would bind only to something unique about Alzheimer's disease itself; the abnormal proteins, beta amyloid, and the abnormal proteins of neurofibrillary tangles," he said.

Dr. Smith says it is too soon to know whether the PET-scan technique might be practical as an early diagnosis tool for Alzheimer's. But at least, he says, researchers have proved early diagnosis is possible.