parkinsonism

Parkinsonism: see Parkinson's disease.

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parkinsonism

Neurological disorder causing progressive loss of control of movement. It was first described in 1817 by British physician James Parkinson (1755–1824). The cause of primary parkinsonism, or Parkinson disease, is unknown. The mean age of onset is about 57, but juvenile parkinsonism is also known. Neurons in the brain that normally produce dopamine deteriorate. When 60–80% are destroyed, signals suppressing unintended movement are disrupted and symptoms appear, including tremor at rest, muscle rigidity, trouble in starting movements, and loss of balance. Known causes include sleeping sickness; certain poisons; repeated blows to the head, as in boxing; and the drug MPTP. Environmental toxins or genetic susceptibility may account for some cases. Drug therapy requires careful scheduling and combinations to delay development of tolerance and side effects. Surgical pallidotomy (destruction of the globus pallidus, a brain structure involved in motor control) and transplantation of fetal dopamine-producing tissue remain experimental.

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parkinsonism [′pär·kən·sə‚niz·əm]

(medicine)

A clinical state characterized by tremor at a rate of three to eight tremors per second, with “pill-rolling” movements of the thumb common, muscular rigidity, dyskinesia, hypokinesia, and reduction in number of spontaneous and autonomic movements; produces a masked facies, disturbances of posture, gait, balance, speech, swallowing, and muscular strength. Also known as paralysis agitans; Parkinson's disease.