Feasibility Study to Evaluate Deep Brain Stimulation (DBS) Settings for the Treatment of Parkinson's Disease

Inclusion Criteria: * Patient is able and willing to provide informed consent to participate in the study. * The patient's implanted DBS system shall be the Medtronic, Inc. Activa® System. The Medtronic Activa System may consists of either, Soletra®, Kinetra® Activa® RC, or Activa® PC Neurostimulator(s) and two DBS Leads (Model 3387 or 3389). * Patient shall have bilateral DBS of the subthalamic nucleolus (STN). * Patient shall have stable DBS stimulation without changes in stimulation parameters for no less than 3 months prior to enrollment. * Patient shall have stable and optimal regimen of antiparkinson drug therapy for no less than 3 months prior to enrollment. * Patient, and caregiver if applicable, is able and willing to be available for study visits throughout the duration of the study (e.g. no planned relocation of residence or extended vacation during the study that would prevent compliance with study visit schedule). * Availability, from the patient's medical records, of a Pre-op MRI and high resolution CT with artifact reduction no less than six (6) weeks post-op. * Patient shall have Hoehn and Yahr stage III or worse when off stimulation and off medication. * Patient shall have demonstrated good response to L-DOPA, defined as no less than a 30% improvement in a UPDRS-III motor exam following the administration of L-DOPA during their screening neurological exam. * Patient shall have demonstrated good response to DBS following the administration of DBS while off medication, defined as an improvement in UPDRS-III motor scores better than their improvement to L-DOPA (as determine in above) or no less than 20% worse of an improvement. Exclusion Criteria: * Evidence of secondary or atypical Parkinsonism as suggested by: stroke, encephalitis, exposure to toxins, neuroleptic antipsychotics, neurologic signs of upper motor neuron or cerebellar involvement, or supranuclear palsy. * Dementia as evidenced by a mini-mental state examination of 24 or below (MMSE ≥ 24). * Prior participation in the Intelect Medical GUIDE study.