Chemical imbalance found by researchers in brains of Alzheimer's patients

April 28, 1993|By Los Angeles Times

PASADENA, Calif. -- Researchers say they have identified previously unsuspected chemical imbalance in the brains of patients with Alzheimer's disease and have developed a sophisticated test that permits quick diagnosis of the disorder.

Early diagnosis of Alzheimer's, which affects as many as 4 million Americans, is becoming increasingly important as researchers develop new drugs that they hope can impede the progress of the disease. Most researchers feel that these drugs will be most valuable when used in the early stages of Alzheimer's, but early detection is now extremely difficult.

Dr. Brian D. Ross, a neurologist at the Huntington Medical Research Institutes in Pasadena, and his colleagues have modified a magnetic resonance scanner to look for chemical differences between the brains of Alzheimer's patients and healthy individuals.

They report today in the journal Radiology that they found an increase in the concentration of the sugar myo-inositol in the Alzheimer's brains and a decrease in another chemical, called N-acetylaspartate or NAA. This combination of changes seems to be unique to Alzheimer's disease and could provide the basis of a technique for quick diagnosis of the disorder.

Alzheimer's disease is now diagnosed by the exclusion of all other possible brain disorders, as well as by a battery of mental-function and neurophyschological tests -- a process that is time-consuming and expensive. A definitive diagnosis can often be made only after death, when an autopsy discloses the extensive plaques and tangles in the brain that are characteristic of the disease.

They do not yet know whether the changes are related to the biology of Alzheimer's or whether they are a secondary effect, Dr. Ross said. But if it is the former, then the discovery could open the door to new forms of therapy for the disease.

"This obviously has to be replicated, but it is very promising," said Dr. Michael Weiner, director of the magnetic resonance unit the San Francisco Veterans Affairs Hospital. "We're excited about the possibility that this might be used in clinical evaluation of Alzheimer's disease, but at this time, we must emphasize that it is still a research tool."

Added Dr. Richard J. Wurtman, director of the Clinical Research Center at the Massachusetts Institute of Technology and an expert in

the biochemistry of Alzheimer's, "If it's confirmed, it could be quite interesting."

Alzheimer's disease primarily strikes people over the age of 65 and is characterized by memory loss, disorientation, depression and deterioration of bodily functions. It is ultimately fatal, causing about 100,000 deaths in the United States each year.

Several researchers have recently reported that they can use magnetic resonance imaging, which produces pictures of the brain, and another technique called PET scanning to diagnose Alzheimer's by detecting areas of cell death associated with it, but these techniques are not in clinical use yet.

Furthermore, Dr. Weiner said, because the changes in brain structure monitored by these techniques are very subtle, both MRI and PET are much less sensitive for diagnosing Alzheimer's than magnetic resonance scanning, which detects the levels of individual chemicals within the brain.

The biggest problem with Dr. Ross's study, he acknowledges, is that the study group is small -- 11 patients who were already known to have Alzheimer's and 10 healthy individuals. Dr. Ross is now gearing up to study more patients.

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