- Subject's PD diagnosis is unclear or there is a suspicion that the subject has a Parkinsonian syndrome such as secondary Parkinsonism (e.g., caused by drugs, toxins, infectious agents, vascular disease, trauma, brain neoplasm), Parkinson-plus syndrome (e.g., Multiple System Atrophy, Progressive Supranuclear Palsy, Diffuse Lewy Body Disease, Corticobasilar Degeneration), or other neurodegenerative disease that might mimic the symptoms of PD.