New Look at Deep Brain Stimulation for Parkinson's

June 3, 2010 -- A comparison of two types of deep brain stimulation shows they are equally effective in improving motor function in Parkinson's disease patients.

Deep brain stimulation involves surgically implanting a device that sends electrical impulses to certain sections of the brain. These electrical impulses stimulate parts of the brain that contribute to Parkinson's disease.

The electrodes are commonly placed in one of two targets: the globus pallidus or the subthalamic nucleus. Both of these areas of the brain are associated with motor function.

A team of researchers, many of them from Veterans Affairs facilities, wanted to learn whether targeting the globus pallidus or the subthalamic nucleus produced better results for Parkinson's disease patients. The study appears in the New England Journal of Medicine.

Parkinson's disease is a disorder of the nervous system that progresses over time. The disease causes the loss of dopamine-producing brain cells.

Dopamine is a chemical produced by the brain that is critical for cognitive function and movement. The symptoms of Parkinson's disease include difficulty moving, tremors, and stiffness in the arms and legs. There is no cure for Parkinson's disease, but it can be managed with treatment.

An estimated 1 million Americans have Parkinson's disease; 4% of patients are diagnosed before age 50.

No Difference Between Treatments

A total of 299 Parkinson's disease patients at seven Veterans Affairs and six university hospitals were randomly assigned to undergo deep brain stimulation of the globus pallidus (152 patients) or  the subthalamic nucleus (147 patients). The effects of the deep brain stimulation were assessed while patients were both on and off their medications.

The patients' outcomes were compared after two years of treatment. The researchers were primarily focused on how motor function improved between the two groups, but they also evaluated the patients' quality of life, including depression, cognitive function, and side effects.

After two years, the researchers did not find significant differences between the two groups.

• Two-thirds of patients in the two groups showed an improvement in motor function while receiving stimulation and off their medication.
• 51% of those undergoing globus pallidus stimulation and 56% of those undergoing subthalamic nucleus stimulation reported side effects.
• Patients undergoing subthalamic nucleus stimulation required lower doses of dopamine medication.
• Depression worsened among those who underwent subthalamic nucleus stimulation but improved among those who underwent globus pallidus stimulation.
• Cognitive function was about the same in both groups except for the speed processing index, which is the ability to focus attention and quickly scan for information; the subthalamic nucleus stimulation group experienced a greater decline compared with the globus pallidus treatment group.
• Both groups reported improvements in quality of life.

The researchers conclude that "both sites [globus pallidus and subthalamic nucleus] are feasible targets," for treatment. "The absence of a difference in motor outcomes in the two study groups should serve to reassure clinicians that the choice of target need not focus solely on improvement in motor function."