People with Parkinson's disease often feel like prisoners in their own bodies -- powerless to control the twitching, jerking and shaking that are common to the disease.

Many of these telltale symptoms are actually caused by drugs used to treat the condition. But a study published Tuesday in the Journal of the American Medical Association (JAMA) indicates that a long-established therapy called deep brain stimulation -- which uses a device made by Fridley-based Medtronic Inc. -- works just as well as drugs in improving Parkinson's patients' quality of life.

The clinical trial, which was sponsored by Medtronic, is the largest of its kind to study the therapy and may change the way doctors treat Parkinson's, which afflicts some 1.5 million Americans.

"This study adds an extra layer of rigor, and more scientific evidence about this therapy,'' said Dr. William Marks Jr., an associate professor of neurology at the University of California-San Francisco, and a principal investigator in the study.

One of the challenges facing deep brain stimulation is that no randomized, controlled studies have been conducted so far comparing it head-to-head against drug therapy.

The results of the 255-patient clinical trial are unlikely to surprise specialists who commonly treat Parkinson's patients. But publication of the study in the prestigious medical journal could spread the word to primary care doctors, and to patients themselves, said Dr. Frances Weaver, one of the primary investigators in the study.

"Now I think patients will at least consider [deep brain stimulation],'' said Weaver, of Northwestern University's Department of Neurology. "Whether they actually qualify and do it is another question.''

The JAMA publication will cause "a buzz of renewed interest and favorable feelings about this surgery,'' said Dr. Martha Nance, a neurologist and director of the Struthers Parkinson's Center in Golden Valley, who was not affiliated with the Medtronic study. "There's been a sense that this is a last-ditch procedure, a treatment for advanced Parkinson's when you've run out of options."

Deep brain stimulation involves two surgical procedures -- one to implant a pacemaker-like device in the chest and the other to insert insulated wires into key areas of the brain. The device in the chest sends tiny jolts of electricity to the brain to control Parkinson's symptoms. The procedure costs $60,000.

The therapy, approved by the Food and Drug Administration in 2002, does not cure the disease, but helps mitigate symptoms associated with it.

Once diagnosed with Parkinson's, most patients are treated with drugs such as Levodopa (or L-dopa), which initially works well at controlling the disease's symptoms. But after five to 10 years, the drugs may cause involuntary uncontrollable movements, called dyskinesia.

Many patients divide their days between "on" and "off" times -- periods when their motor symptoms are under control or out of control -- depending on the potency of the medication in their system.

The JAMA study indicated that the deep brain stimulation patients gained an average of 4.6 hours a day of "on" time, compared with no gain for those treated with drugs.

Richard Chan, a 43-year-old San Francisco resident who was part of the study, said drugs worked at first for him, but eventually their potency began to wear off. So he took more. "I was on everything,'' he said, rattling off a list of drug names. "But it got to the point where it was unbearable."

Although the study largely highlights the positive effects of the therapy, an editorial in the same issue of JAMA written by Dr. Günther Deuschl, a German neurologist, points out that surgery to implant the leads and neurostimulator carries some measure of risk.

Patients in the study who were treated with deep brain stimulation reported 659 moderate or severe "adverse events" related to the treatment, including one death following surgery, while those treated with drugs reported 236 events.

Weaver said one complication she noticed in the group was that a number of patients fell down following surgery. "We think it's because they felt so much better, they were more active, because with Parkinson's balance is an issue," she said. One patient fell off a roof after making repairs and broke both his legs, she said.

Chan said he could walk before his brain surgery, but he was shaking so much that he found it difficult to keep his balance. After surgery, that changed. "I felt like a newborn baby," he said. Rudimentary tasks that were once impossible are now part of his daily routine, including changing his clothes, bathing and even working out in the gym.

"I can bench-press over 200 pounds," he said.

Janet Moore • 612-673-7752