The purpose of this prospective, participant-blinded trial is to determine the changes in sleep architecture in a cohort of subjects who have undergone deep brain stimulation (DBS) surgery for treatment of movement disorders such as moderate to advanced Parkinson's disease (PD), tremor, or dystonia. Our preliminary observational data suggest that unilateral subthalamic nucleus (STN) DBS improves subjective sleep quality in PD patients 6 months after the procedure. The cause of this improvement in sleep quality is unknown, and this study proposes the use of polysomnography (PSG) to test whether the improvement in sleep is independent of improvement in night-time mobility associated with DBS treatment of the motor symptoms of PD, tremor, or dystonia.

Inclusion Criteria:

• Prior DBS surgery for treatment of movement disorders such as PD, tremor, or dystonia.
• Stable DBS stimulator settings and medication regimen for at least 6 weeks prior to the sleep studies.
• Sleep dysfunction as measured by the Pittsburgh Sleep Quality Index (PSQI) (score >5) at the subject's baseline pre-surgical evaluation.

Exclusion Criteria:

• Known narcolepsy
• Other previous surgical treatment of Parkinson's disease, tremor, or dystonia (with the exception of DBS) including pallidotomy, thalamotomy, or gene therapy procedures.
• Untreated obstructive sleep apnea. If obstructive sleep apnea is discovered during the first sleep study, the subject will be removed from the study. After they have been treated for at least 6 weeks with CPAP, they can re-start the study.