MONDAY, Aug. 8 (HealthDay News) -- The benefit of deep brain stimulation in controlling tremors and improving motor function for those with Parkinson's disease appears to last at least 10 years, according to a small new study by Canadian researchers.

Parkinson's disease is one of several conditions called motor system disorders, which are caused by the loss of dopamine-producing brain cells. The main symptoms of Parkinson's disease are tremors or trembling in hands, arms, legs, jaw and face; rigidity or stiffness of the limbs and trunk; slowed movement; and impaired balance and coordination.

As the disease progresses, patients can have difficulty walking, talking or doing other simple tasks, according to the U.S. National Institute of Neurological Disorders and Stroke.

In deep brain stimulation, a surgeon implants a small device called a neurostimulator under the skin near the collar bone. The doctor then positions wires from the device with electrodes on their ends in areas of the brain that control motor function. The device works by electrically stimulating these areas, blocking abnormal nerve signals that cause the tremor in Parkinson's disease patients.

"Deep brain stimulation is still effective in improving motor signs in advanced Parkinson's disease patients 10 years after the surgery," said lead researcher Dr. Elena Moro, an assistant professor of neurology at the University of Toronto.

"However, this surgery does not stop the slow progression of the disease over time, as documented by the progressive loss of benefit that both deep brain stimulation and the drug levodopa show in improving walking, balance and speech over the years," she said. (Levodopa combined with carbidopa is the most widely used drug treatment for Parkinson's disease.)

Parkinson's disease patients who are considering deep brain stimulation surgery should always ask their doctor how long the benefit lasts after surgery, Moro said. "Our study can provide both patients and physicians with this important answer," she said.

"Deep brain stimulation is not a cure but a symptomatic treatment," Moro said. "Parkinson's disease progresses over time."

Although deep brain stimulation is considered safe, like all surgeries it carries some risks. Complications and side effects of the surgery can include infection, bleeding in the brain, stroke, seizures, speech and breathing problems, and heart problems, according to Mayo Clinic. The report noted that two of the patients in the study developed a serious device-related infection between 5 and 10 years after surgery.

The report was published in the Aug. 8 online edition of the Archives of Neurology.

For the study, Moro and colleagues examined 18 patients with advanced Parkinson's disease who were given implants for deep brain stimulation in 1996 to 2000. The researchers assessed the patients' motor function before implanting the device and again after one, five and 10 years.

At the 10-year assessment, Moro's team found that deep brain stimulation, along with medication, was tied to significantly better motor function. However, there was some progressive worsening of walking, posture and balance, the researchers found.

The authors also noted that the study's limitations included its small size and the lack of a control group.

Commenting on the study, Dr. Michael S. Okun, medical director of the National Parkinson Foundation, said that "this paper is important as it underscores the potential long-term benefits that may be achieved with deep brain stimulation."

The paper also shows that Parkinson's disease progressed despite the deep brain stimulation, Okun said. "Patients should be aware that deep brain stimulation is a potent symptomatic therapy with long-term benefits, but is not a cure," he concluded.

Another expert, Frances Weaver, director of the Center for Management of Complex Chronic Care at the Hines VA Hospital in Illinois, said these results might not apply to all patients with Parkinson's disease.

This group of patients was relatively young, she said. They were diagnosed with Parkinson's disease at an average age of 40 and received treatment with deep brain stimulation when they were in their 50s, she said.

"The majority of persons with Parkinson's are diagnosed in their 60s," Weaver said. "This study includes a younger sample, likely representing more early-onset Parkinson's disease patients, and the results may not generalize to the overall Parkinson's disease population," she said.

Currently, there is no cure for Parkinson's disease and treatment is focused on treating its symptoms.

More information

For more information on Parkinson's, visit the U.S. National Institute of Neurological Disorders and Stroke.