Parkinsonism is a generic term for a neurologic syndrome of rigidity and bradykinesia, with or without other symptoms such as tremor. There are many underlying causes of parkinsonism, all involving some level of dysfunction of the basal ganglia. Parkinson disease is the most common neurodegenerative cause of parkinsonism; other neurodegenerative causes include "atypical Parkinson" or "Parkinson plus" syndromes, such as multisystem atrophy, corticobasal syndrome, progressive supranuclear palsy, and Lewy body dementia.

Parkinsonism can also result from medications (drug-induced parkinsonism), especially the dopamine receptor blocking agents such as the antipsychotics and antiemetics. It can result from certain toxins (such as carbon monoxide and organic solvents) as well as metabolic abnormalities (hypoparathyroidism). Structural injuries – chronic repetitive head trauma, hydrocephalus, subcortical small vessel ischemic vasculopathy ("vascular parkinsonism") – can also produce parkinsonism.

Thus the prognosis is variable, from static to progressive, depending on the etiology. Other symptoms and signs along with predisposing medical history and risk factors can yield valuable clues to the etiology.

Related topic: drug-induced movement disorders