In general, the neurologic diseases that are classified as extrapyramidal disorders are characterized by the presence of involuntary movements. The structures involved in producing extrapyramidal diseases are, for the most part, the basal ganglia.1.2
Parkinsonism is the most common of the extrapyramidal disorders; prevalence is estimated at 1% of the population over age 50 years, and approximately 36,000 new cases are identified each year. The disease is characterized by rigidity of trunk, limbs, and head; by resting or occasionally intention tremor of the head or limbs, usually the hands; and by bradykinesia, or slowness in initiating voluntary movements. Presence of one component of the triad of rigidity, tremor, and bradykinesia suggests the disease and constitutes the minimal clinical criterion for diagnosis.But the clinical array of signs in parkinsonism is often much broader than the triad cited, and various other features that affect prognosis can be
Poser CM, Alter M, Currier RD, Hunter SE. Common Demyelinating and Degenerative Diseases and Extrapyramidal Disorders—Panel 4. Arch Neurol. 1979;36(12):759–770. doi:10.1001/archneur.1979.00500480033006
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