Degenerative Nigrostriatal Dysfunction in Drug-induced Parkinsonism

Parkinson's disease (PD) and Drug-induced Parkinsonism (DIP) can be clinically indistinguishable and DIP sometimes represents "unmasking of underlying PD. The objective of this study is to determine the relationship of underlying Parkinson's disease (PD) to the incidence and clinical outcome in DIP using non-motor assessments as a marker for nigrostriatal degeneration.

Research Design: This is a nested case-control design to investigate risk factors associated with the development of DIP and persistent Parkinsonism after antipsychotic (AP) withdrawal (a potential clinical marker of underlying PD). Target enrollment is 45 subjects.

Methodology: We will examine objective olfactory function (via objective olfactory testing), other non-motor symptoms of PD (via standardized validated questionnaires), and motor findings (via clinical exam and quantitative gait analysis) in: 1) DIP patients (30 subjects) compared to AP-treated patients without Parkinsonism (15 subjects) and 2) patients with persistent Parkinsonism compared to those whose symptoms resolve in the DIP cohort followed prospectively after a change in AP treatment. Additionally, in patients where it was performed clinically, we will evaluate dopamine transporter SPECT imaging (DaTI) as a marker of nigrostriatal integrity examining the ability of qualitative and semi-quantitative analysis to distinguish between pharmacologic and degenerative Parkinsonism. We will also measure serum uric acid and Apolipoprotein A1, two putative biomarkers in early PD, and examine their relationship with clinical and radiologic status.