Abbreviation: PD
A neurodegenerative disease involving a progressive depletion of dopaminergic neurons in the basal ganglia, particularly the substantia nigra. The typical clinical picture seen in PD is called "parkinsonism" and features the classical cardinal symptom of bradykinesia along with resting tremor and/or rigidity. Postural instability is another frequent late finding. Neuropsychiatric and nonmotor manifestations include cognitive dysfunction, depression, and psychosis.