Summary

parkinson_disease is a progressive_neurodegeneration of the basal_ganglia with dopamine_loss in the substantia_nigra. Core motor features are bradykinesia, rigidity, resting_tremor, and postural_instability. Early signs include decreased arm swing and masked facies. Common nonmotor_symptoms include constipation, sleep problems, depression, and anosmia. Onset is usually gradual and asymmetric. Diagnosis is clinical, based on motor features and history. Progression varies, but symptoms typically worsen over time.