WEDNESDAY, Nov. 12, 2003 (HealthDayNews) -- Deep-brain stimulation using implanted electrodes provides substantial, lasting benefits for patients with severe Parkinson's disease, with a significant "but," says a report by the French scientists who pioneered the technique.
The first 49 patients to have the implants "had marked improvement over five years while off medication," reads the report in the Nov. 13 issue of the New England Journal of Medicine by neurologists at the University of Grenoble.
But the implants do not prevent the worsening of speech, instability, uncontrolled motions and other symptoms that also occur in patients who take levodopa, the standard drug treatment for the neurological condition, the researchers report.
Levodopa increases brain levels of dopamine, an enzyme essential to nerve cell function. It remains "the gold standard" for drug treatment of Parkinson's disease, says Dr. Anthony E. Lang, a professor of neurology at the University of Toronto, who wrote an accompanying editorial. But the effects of levodopa can start to fluctuate erratically in some patients, rendering them helpless. The implanted electrode technique was developed for those patients.
The optimistic aspect of the French study of the implants is that "it shows that excellent responses can be sustained over a course of five or more years for that kind of patient," says Lang, who reported similar results in a smaller study earlier this year.
"But what we learn from the implant studies is that if you control all the dopamine-related problems, other things begin to become more evident," he says. "This shows a need for refocusing of attempts to develop new treatments for Parkinson's disease, treatments that affect not only the dopamine system but also other areas of brain function."
One problem is the development of dementia, the loss of mental function seen in Alzheimer's disease, Lang says. Three patients in the French study developed dementia.
The real hindrance in the way of new treatments is that no one really knows what goes wrong in Parkinson's disease, Lang says. Attempts at gene therapy and stem cell implants have not been effective thus far, he says.
The relative success of the electrode implant technique means it should be used more aggressively, before patients on levodopa develop major disabilities that leave them bedridden and helpless. "What you want to do is to prevent all those problems before they occur," Lang says, and implanted electrodes can accomplish that in many patients.
But deep-brain stimulation requires a skilled surgical team and carries surgical risks that require careful screening of patients. The French study included only relatively young Parkinson's patients, with an average age of 55, who were carefully screened for dementia and psychiatric problems.
"Despite the careful screening, one patient committed suicide," Lang notes.
Cost is also an issue. Even in Canada, which has national health insurance, hospital administrators are concerned about the high cost of the implants.. "We need to develop therapies that are less costly, more effective and work in an increasing number of people," he says.
More information
An overview of Parkinson's disease is given by the National Institute of Neurological Diseases and Stroke or the National Parkinson Foundation.
