The objective of this study is to evaluate the effectiveness of Deep Brain Stimulation as an adjunctive treatment for reducing some of the symptoms of advanced, levodopa-responsive Parkinson's disease that are not adequately controlled with medication.

It is the first study in Parkinson patients outside the US with a Deep Brain Stimulation system using constant current instead of constant voltage and using a lead with an active electrode tip.

This study is designed as a prospective, observational, non-randomized, multi-centered study for 12 months in duration from implantation with the subjects being used as their own control. The primary outcome assessment will occur at three months: however, subjects will be followed for one year.

A comparison of measures within the same person from pre-treatment to post-treatment will be performed. Also, pre-treatment and post-treatment group means and standard deviations will be determined.

Inclusion Criteria:

Subjects enrolled in this study must meet the following inclusion criteria:

1. Subject has signed an informed consent.
2. Subject has been diagnosed, by a neurologist, with idiopathic Parkinson's disease.
3. Subject is a candidate for surgery.
4. Subject is 18 to 80 years of age.
5. Subject has a history of improvement of Parkinson's symptoms as a direct result of administering l-dopa to the subject with at least a 25% improvement in Unified Parkinson's Disease Rating Scale (UPDRS) motor score or subject has been diagnosed with tremor-dominant Parkinson's disease.
6. Subject should be stable on anti-Parkinson's disease medication for at least one month prior to study enrollment.

Exclusion Criteria:

Subjects will be excluded from the study if they meet any of the following criteria:

1. Subject has any major illness or medical condition that in the opinion of the physician would interfere with participation in the study.
2. Subject has non-treated clinically significant depression or any other significant psychiatric co-morbidities.
3. Subject has any condition requiring repeated MRI scans;
4. Subject has any condition requiring diathermy;
5. Subject is on anticoagulant medications and is unable to interrupt for time of procedure.
6. Subject has a history of cranial surgery.
7. Subject has dementia that interferes with their ability to co-operate or comply with study requirements or comprehend the Informed Consent as determined by the investigator.
8. Subject abuses drugs or alcohol.
9. Subject has a history of seizure
10. Subject has confirmation of diagnosis of a terminal illness associated with survival <12 months.
11. Female that is lactating or of childbearing potential with positive urine pregnancy test or not using adequate birth control.
12. Subject has participated in a drug, device or biological trial within the preceding 30 days.

Libra™/LibraXP™ DBS System Eligible subjects in this study will be screened to confirm that they meet the strict guidelines for advanced, levodopa-responsive Parkinson's disease that are not adequately controlled with medication followed by surgery to implant the Libra™/LibraXP™ deep brain simulation system.