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Myoclonus +mI-!@-klu-nus

by Hector A. Gonzalez-Usigli, MD, Alberto Espay, MD

Myoclonus refers to quick, lightning-like jerks (contractions) of a muscle or a group of muscles.

Myoclonus may involve only one hand, a group of muscles in the upper arm or leg, or a group of facial muscles. Or it may involve many muscles at the same time.

Myoclonus may occur normally, often when a person is falling asleep. For example, as people start to doze off, they may jerk awake (as if startled), or muscles in part of the body may twitch. However, in some cases, myoclonus may result from a disorder, such as the following:

  • Liver failure

  • Kidney failure

  • Brain damage due to a virus or cardiac arrest (when the heart's pumping stops suddenly)

  • Metabolic disorders (such a high or low blood sugar level or low levels of calcium, magnesium, or sodium)

  • Oxygen deprivation

  • Head injuries

  • Alzheimer disease (occasionally)

  • Creutzfeldt-Jakob disease

  • Seizure disorders (such as juvenile myoclonic epilepsy)

Myoclonus can occur after a person takes high doses of certain drugs such as antihistamines, some antidepressants (such as amitriptyline), bismuth, levodopa (used for Parkinson disease), or opioids (narcotic pain relievers).

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