
INTRODUCTION
Parkinson’s disease (PD) is a chronic, progressive neurodegenerative disorder characterized by four cardinal features: tremor at rest, rigidity, bradykinesia, and postural instability. PD results from a loss of dopaminergic neurons in the substantia nigra pars compacta. Approximately one million Americans currently have PD, and an estimated 40,000 new cases are diagnosed each year. In most cases, the diagnosis is confirmed in persons 50 years of age and older. The incidence of PD rises with increasing age.




















