Studies have shown that a "brain pacemaker" called deep brain stimulation (DBS) is an effective treatment for Parkinson's disease. But there's been debate over what region of the brain to stimulate: the globus pallidus interna or the subthalamic nucleus. Now, a major study published in the June 3, 2010 New England Journal of Medicine is showing that stimulating either region resulted in similar improvements in motor function. There were small differences in non-motor effects such as mood and cognitive function. "Both targets in the brain are viable for improving motor function. This is great news for patients," said Frances Weaver, PhD, of Edward Hines Jr. VA Hospital and Loyola University Health System. Weaver, one of the study's lead investigators, is a professor and director of the Program in Health Research at Loyola University Chicago Stritch School of Medicine and director of the Center for Management of Complex Chronic Care at Hines VA Hospital. DBS is a treatment for Parkinson's patients who no longer benefit from drugs or who experience unacceptable side effects. DBS is not a cure, and it does not stop the disease from progressing. But in the right patients, DBS can significantly improve symptoms, especially tremors. DBS also can reduce rigidity. "DBS increases the percentage of time that a patient is functional," said Loyola neurosurgeon and professor in the Department of Neurological Surgery, Dr. Douglas Anderson, who has an active practice in DBS and movement disorders. "It also improves a patient's ability to move arms or legs in a more coordinated fashion. And there is a lessening of bradykinesia [slowness of motion]." In the DBS procedure, a neurosurgeon drills a dime-size hole in the skull and inserts an electrode about four inches into the brain. A connecting wire from the electrode runs under the skin to a battery implanted near the collarbone. The electrode delivers mild electrical signals that effectively reorganize the brain's electrical impulses. The procedure can be done on one or both sides of the brain. Weaver was first author of a pivotal 2009 study, published in the Journal of the American Medical Association, which found that DBS was more effective than medications in treating patients with advanced Parkinson's disease. The new study included 299 Parkinson's disease patients at 7 VA and 6 university hospitals. Patients were randomly assigned to receive DBS in either the globus pallidus interna or subthalamic nucleus. While there were no significant differences in motor function, researchers did find differences in other areas. Patients who received subthalamic stimulation required lower doses of L-dopa medications. But the subthalamic group also had slower visuomotor speed, which measures how quickly a patient thinks and acts on information. Also, depression got worse in the subthalamic group, but lessoned in the pallidal group. "Based on the findings of this study, we expect that doctors will consider factors other than motor function when deciding what region of the brain to target," Weaver said.
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