Adaptive Deep Brain Stimulation for Freezing of Gait in Parkinson's Disease

Inclusion Criteria: 1. Ability to give informed consent for the study 2. Movement disorder symptoms that are sufficiently severe, in spite of best medical therapy, to warrant surgical implantation of deep brain stimulators according to standard clinical criteria 3. Patient has requested surgical intervention with deep brain stimulation for their disorder 4. No magnetic resonance (MR) abnormalities that suggest an alternative diagnosis or contraindicate surgery 5. Absence of significant cognitive impairment (score of 21 or greater on the Montreal Cognitive Assessment (MoCA)), 6. Signed informed consent 7. Ability to comply with study follow-up visits for brain recording, testing of adaptive stimulation, and clinical assessment. 8. Age 21-75 9. Diagnosis of idiopathic PD with duration of motor symptoms for 3 years or greater 10. Patient has undergone appropriate therapy with oral medications with inadequate relief as determined by a movement disorders neurologist. 11. UPDRS-III score off medication between 20 and 80 and an improvement of at least 30% in the baseline UPDRS-III on medication score, compared to the baseline off-medication score, and motor fluctuations with at least 2 hours per day of on time without dyskinesia or with non-bothersome dyskinesia. OR Patients with tremor-dominant PD (a tremor score of at least 2 on a UPDRS-III sub-score for tremor), treatment resistant, with significant functional disability despite maximal medical management 12. Patients with gait impairments including freezing of gait off medication. 13. Ability of patient and/or caregivers to recharge the system evaluated by all clinicians and study personnel. Exclusion Criteria: 1. Coagulopathy, anticoagulant medications, uncontrolled hypertension, history of seizures, heart disease, or other medical conditions considered to place the patient at elevated risk for surgical complications 2. Evidence of a psychogenic movement disorder: Motor symptoms that remit with suggestion or "while unobserved", symptoms that are inconsistent over time or incongruent with clinical condition, plus other manifestation such as "false" signs, multiple somatizations, or obvious psychiatric disturbance. 3. Pregnancy: all women of child bearing potential will have a negative urine pregnancy test prior to undergoing their surgical procedure. 4. Significant untreated depression (BDI-II score \>20). History of suicidal attempt or active suicidal ideation (Yes to #2-5 on C-SSRS) 5. Any personality or mood symptoms that study personnel believe will interfere with study requirements. 6. Subjects who require Electroconvulsive therapy (ECT), Repetitive Transcranial Magnetic Stimulation (rTMS) or diathermy 7. Implanted stimulation systems such as cochlear implant, pacemaker, defibrillator, or neurostimulator 8. Previous cranial surgery 9. Drug or alcohol abuse 10. Meets criteria for Parkinson's disease with mild cognitive impairment (PD-MCI). These criteria are performance of more than two standard deviations below appropriate norms, for tests from two or more of these five cognitive domains: attention, executive function, language, memory, and visuospatial tests. 11. Known allergies to the implantable device components including titanium, polyurethane, silicone, and nylon.