People with Parkinson's disease improve their motor function equally well with either of two types of deep brain stimulation, a new study shows.

In deep brain stimulation, a device is surgically implanted to send electrical impulses to certain sections of the brain.

For Parkinson's, the electrodes are placed on the globus pallidus or the subthalamic nucleus, two areas associated with motor function.

In Thursday's issue of the New England Journal of Medicine, researchers reported 299 patients randomly assigned to receive deep brain stimulation (DBS) at either site experienced comparable benefits for the motor symptoms of Parkinson's, such as tremors, after two years.

Dr. Kenneth Follet, chief of neurosurgery at the University of Nebraska Medical Center in Omaha, and his colleagues assessed the effects of the deep brain stimulation.

Equivalent for tremor, stiffness

"We found that motor outcomes between the two groups were not significantly different," Follett said in a release.

"These results establish that DBS delivered to these two brain areas linked to key motor control pathways can have equivalent effects on tremor, stiffness and other motor symptoms of Parkinson's disease," agreed Dr. Walter Koroshetz, deputy director at the U.S. National Institute of Neurological Disorders and Stroke, one of the funders of the study.

Two-thirds of patients in the two groups showed an improvement in motor function while receiving stimulation and off their medication.

Overall, about half of the patients had serious side-effects. The most common was infection at the incision site, which resolved in 99 per cent of participants by the end of the two-year study.

Quality of life considered

Both groups also reported similar improvements in quality of life. There were modest differences in mood and cognitive function between the two groups, Follett said.

Motor control problems such as shaking, rigidity, slowed movement and poor balance are often the first symptoms of Parkinson's disease. In later stages, patients develop a variety of cognitive and mood problems, including depression, apathy, slowed thinking, confusion, impaired memory and trouble sleeping.

Doctors and patients can choose between the two types of DBS based on the motor and non-motor symptoms affecting quality of life, Follett advised.

The investigators will continue to follow participants for several more years to look at motor function and quality of life over the long term, as well as the need to replace electronics.

It's estimated that approximately 100,000 Canadians have Parkinson's disease.

The study was also funded by the U.S. Department of Veterans Affairs, with additional support from Medtronic, Inc., the makers of the DBS systems used in the study.