Inclusion Criteria:
General:
* English Speaking
* Able and willing to provide informed consent
REM behavior disorder:
* Repeated episodes of sleep-related vocalization and/or complex motor behaviors. These behaviors are documented by polysomnography to occur during REM sleep or, based on clinical history of dream enactment, are presumed to occur during REM sleep.
* Polysomnographic recording demonstrates REM sleep without atonia (RWA).
* The disturbance is not better explained by another sleep disorder, mental disorder, medication, or substance abuse.
Parkinson's disease:
* Meets the Movement Disorders Society criteria for Clinically Probable Parkinson's disease.
* Disease duration \< 10 years 10 years from PD diagnosis at the time subject was first identified to be screened for the study.
Healthy controls:
* No clinical evidence of Parkinson's disease or RBD.
* Normosmic.
Exclusion Criteria:
General:
* Known immune deficiency disorder.
* Personal history of any neurological disorder, including but not limited to:
Multiple Sclerosis, Alzheimer's disease, Multiple System Atrophy, Progressive Supranuclear Palsy, Amyotrophic Lateral Sclerosis, or repeated head trauma.
* Solid or hematological malignancy other than in-situ carcinoma of the cervix or basal cell carcinoma of the skin unless the subject has no evidence of active disease and has not received treatment, including chemotherapy, immunotherapy or radiation treatment within previous 12 months.
* Known blood clotting disorder (with increased likelihood of bleeding).
* Short Bowel Syndrome, Ileostomy, or colostomy
* History of vagotomy.
* Taking anticoagulant or antiplatet medication (coumadin, heparin, apixaban (Eliquis ®), rivaroxaban (Xalreto®), edoxaban (Lixiana®), or dabigatran (Praxeda®). Low-dose (100 mg/day or less) aspirin is allowed. Taking certain drugs that can interfere with interpretation of DaT scan, such as methylphenidate (Ritalin®), stimulant drugs such as phentermine or ephedrine, certain antidepressants, including mazindol, or radaraxine, benztropine (Cogentin®) within 5 half-lives prior to the date of the scheduled DaT scan. Subjects taking a potentially interfering medication can only be included if the medication is stopped with the concurrence of the subject and the prescribing health care provider. Persons taking bupropion or amphetamine will be asked to hold the medicine on the morning of the scan. They will be able to take the medicine the same day after the scan. Inability to hold bupropion or an amphetamine for the scan, however, will not exclude an individual from participating.
* Receiving chemotherapy agents with ability to affect the immune system, or radiation therapy (within the past 12 months).
* Receiving potent immunosuppressant agents (e.g., anti-TNF, or IL-6 antibodies, JAK/STAT inhibitors, chemotherapy agents such as methotrexate or Cytoxan used to induce immunosuppression), Use of low, maintenance doses of corticosteroids may be permitted, depending on the underlying disease indication.
* Treatment with an experimental agent within 3 months of screening.
* Pregnancy or actively breast feeding.
* Treatment of thyroid disease with radioactive iodine.
* Lidocaine allergy.
Additional Exclusion Criteria for Subjects with diagnosis of PD:
* Meets any of the MDS exclusionary criteria for PD diagnosis. Additional Exclusion Criteria for Subjects with RBD
* An identified secondary cause of RBD.
* Neurodegenerative Disease: Neurological examination must be performed to exclude parkinsonism (according to MDS PD criteria), and clinically evident dementia.
* Secondary RBD, caused by antidepressant medications (antidepressant- triggered RBD can be included provided that diagnosis is documented of antidepressant medications, and patients can be taking antidepressants during the study).
* Diagnosis of narcolepsy. Additional Exclusion Criteria for Healthy Control Subjects
* History of Parkinson's disease in a first-degree blood relative.
