Brain picture reveals signs of Parkinson's

Examining levels of chemicals can aid in treating disease

April 21, 2002|By William Hathaway & Hilary Waldman | By William Hathaway & Hilary Waldman,Special to the Sun

The first signs of Parkinson's disease are so subtle that they are all but invisible. By the time the telltale tremors appear -- perhaps the shaking of a fork or the unintentional rustling of a newspaper -- the neurological disease has already done more than half its damage.

Now scientists say they have found a way to strip the cloak of invisibility from the debilitating disease that afflicts about 1 million Americans.

Using brain imaging technology, the scientists can take a snapshot of Parkinson's, or, more accurately, levels of dopamine, a key brain chemical that governs motor control and other key functions. In theory, these images can help doctors diagnose and treat the disease before the first symptoms appear and more than half of the dopamine activity in the brain already has been lost.

The imaging test "demystifies the disease for people," said Dr. Kenneth Marek, a neurologist at the Institute for Neurodegenera-tive Disorders, a New Haven, Conn., nonprofit research group that has developed a new radioactive marker used in imaging technology. "If there is one key message, it is that people need to deal with Parkinson's earlier rather than later."

Just recently in the Journal of the American Medical Associa-tion, researchers from the institute who used the imaging technology reported that the drug pramipexole seems to be better than another widely used Parkinson's drug, levodopa, at slowing the loss of dopamine-producing neurons in patients.

"This is at least one method of evaluating" the efficacy of new Parkinson's drugs, said Marek, who is also a principal in a for-profit biotechnology company in New Haven, Molecular Neuro-imaging LLC.

The imaging technique, developed by Marek while he was an associate professor of neurology at Yale University School of Medicine, uses radioactive tags that bind to a dopamine transporter protein on the surface of brain cells. An imaging system called Single Photon Emission Computerized Tomography, or SPECT, detects the tag attached to the dopamine transporter. The pictures give a close approximation of dopamine activity in the brain, Marek said.

The imaging test can discriminate between patients who have Parkinson's and those who don't with 98 percent accuracy, the researchers claim.

Parkinson's disease can kill up to 80 percent of dopamine-producing cells before it is detected. Once the disease becomes established, the symptoms become all too easy to spot. Patients initially have weakness and tremors on one side of the body, but both sides soon become affected.

Current drugs help at first but become less effective. However, dozens of promising new drugs are under development, said Jeanne Rosner, director of educational programs at the Parkinson's Disease Founda-tion, a nonprofit group.

Along with better drugs, SPECT technology is the second major innovation that may help change the way Parkinson's is treated, she said. However, major obstacles must be overcome before SPECT scans are widely used.

Medical scientists have yet to clearly define risk factors for Parkinson's. In most cases, the disease does not appear to be inherited. Exposure to heavy metals seems to be one environmental cause, but the major risk factor seems to be old age.

Without such risk factors, there is no way to know who needs testing. SPECT technology is "not something insurance companies are going to be willing to pay for unless we can find a way to define the population that might benefit," Rosner said.

William Hathaway and Hilary Waldman are reporters for the Hartford Courant, a Tribune Publishing newspaper.

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