Phase II Subthalamic Nucleus (STN) vs. Globus Pallidus (GPi) Trial

The goal of the second phase of the study is to determine if simultaneous bilateral subthalamic nucleus stimulation or simultaneous bilateral globus pallidus stimulation is more effective in reducing symptoms of Parkinson's Disease.

Deep 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 (Phase I) 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 (Phase II) 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 arm patients will then be randomized to proceed into the DBS surgical phase of the trial. The DBS site (STN pr 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 months for DBS only patients and 30 months for BMT-DBS patients) Effective 8/5/05 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.

Eligibility Criteria:
Inclusion Criteria:

* idiopathic Parkinson's Disease
* Hoehn and Yahr stage 2 or worse when off medications
* L-dopa responsive with clearly defined "on" periods (i.e. symptoms improve at least partially with L-dopa administration, a characteristic that helps distinguish idiopathic PD from "Parkinson's Plus" and atypical Parkinson's syndromes-see below)
* persistent disabling symptoms (e.g. on troubling dyskinesias, or disabling "off" periods at least 3 hours/day) despite medication therapy. Patients will have been treated with variable doses of levodopa and dopamine agonists (at a minimum) and will have had an adequate trial of other adjunctive medications)
* stable on medical therapy for at least one month prior to study enrollment
* age \>21
* available and willing to be followed-up according to study protocol

Exclusion Criteria:

* "Parkinson's plus" syndromes, secondary, or atypical Parkinson's syndromes (e.g. progressive supranuclear palsy, striato-nigral degeneration, multiple system atrophy, post-stroke, post-traumatic, or post-encephalitic Parkinson's. These patients have cardinal symptoms characteristic of PD but with additional symptoms indicating other organic brain dysfunction, such as gaze palsies, autonomic dysfunction, lack of response to L-dopa, these individuals tend not to improve with standard treatments for PD)
* previous Parkinson's Disease surgery
* medical contraindications to surgery or stimulation (e.g. uncontrolled hypertension, advanced coronary artery disease, other implanted stimulation or electronically-controlled devices including cardiac demand pacemaker, aneurysm clips, cochlear implants, or a spinal cord stimulator) (Note: for the subject who receives either a pacemaker and/or defibrillator after this study enrollment, he/she will be allowed to continue the study if the neurostimulator system can be adequately programmed to permit system compatibility)
* contraindication to magnetic resonance imaging (e.g. indwelling metal fragments or implants that might be affected by MRI)
* active alcohol or drug abuse
* score on Mini-Mental Status examination of 24 or lower, or other neuropsychological dysfunction 9e.g. dementia) that would contraindicate surgery
* intracranial abnormalities that would contraindicate surgery (e.g. stroke, tumor, vascular abnormality affecting the target area)
* pregnancy
* concurrent participation in another research protocol