Subjects will be asked to attend study visits every 6 months for up to 5 years of follow up. Each visit will consist of patient outcomes questionnaires, neurological exams, computerized assessments of gait and balance, a video recorded motor exam, and biological specimen collection for biomarker discovery.
Inclusion Criteria: - A diagnosis of idiopathic PD meeting UK PD Society Brain Bank Criteria (Step 1, Step 2, and 2 items present from step 3).1 - Male or female age 30 years or older at time of PD diagnosis, Hoehn & Yahr (H&Y) stage I-IV. - Confirmation from I-123 Ioflupane SPECT (DatScan®) of dopamine transporter deficit for de-novo, untreated patients. - Clinical evidence of response to dopaminergic medication (MAO-B inhibitors, dopamine agonists, levodopa, or combinations) in patients on treatment for PD. - Ability to provide written informed consent in accordance with Good Clinical Practice (GCP), International Conference on Harmonization (ICH), and local regulations. - Able to make visits to UT Southwestern every 6 months for up to 5 years without undue hardship. Exclusion Criteria: - Idiopathic PD, H&Y stage 5, as these will be unable to participate in gait assessments. - Confirmed or suspected atypical parkinsonian syndromes due to drugs, metabolic disorders, encephalitis, or degenerative diseases. - Presence of definite dementia (MoCA < 17)2. - For de-novo subjects: received any of the following drugs that might interfere with dopamine transporter SPECT imaging: neuroleptics, metoclopramide, alpha methyldopa, methylphenidate, reserpine, or amphetamine derivative, within 6 months of screening. - For the prospective CSF cohort: current treatment with anticoagulants (e.g., coumadin, heparin) that might preclude safe completion of the lumbar puncture. - For the prospective CSF cohort: any condition that precludes the safe performance of routine lumbar puncture, such as prohibitive lumbar spinal disease, bleeding diathesis, or known clinically significant coagulopathy or thrombocytopenia. - Any other medical or psychiatric condition or lab abnormality, which in the opinion of the investigator might preclude participation.