• time spent in the 'on' state without troubling dyskinesia based on patient motor diaries [ Time Frame: at six months ] [ Designated as safety issue: No ]
  

• Scores on the UPDRS for motor function 'off' medication and 'on' stimulation. [ Time Frame: at two years ] [ Designated as safety issue: No ]
  

Deep BrainDeep Brain Stimulation (DBS) is a promising therapy for Parkinson's disease (PD). Whether DBS is superior to comprehensive best medical therapy or whether some patients or symptoms respond better to DBS in one area of the brain or the other is currently not known.

The goals of this project are to compare the effectiveness of DBS and comprehensive medical therapy as treatments for PD, and to compare bilateral DBS at 2 areas of the brain--the subthalamic nucleus (STN) and the globus pallidus (Gpi)--to determine the most effective brain site for surgical intervention

In this prospective, randomized, multi-center trial, 316 patients will be enrolled at 13 centers over four and a half years. Patients will initially be randomized to immediate surgery (DBS) or to 6 months of "best medical therapy." BMT patients will then proceed into the surgical phase of the trial. The DBS site (STN or GPi) will be assigned on a random basis at the time the patient enters the surgical phase of the trial. Patients will be followed for two years post surgery (24-30 months). Effective 08/05/05, randomization to the BMT arm has been discontinued since the study has sufficient information to compare the outcomes of DBS and BMT patients at 6 months. The findings will be critically important in establishing the optimal surgical treatment of the disabling symptoms of PD.