Myoclonus is a brief and rapid twitching of a muscle or muscle groups. The twitching happens suddenly. It cannot be stopped or controlled.

There are different types of myoclonus. Some occur normally, like the hiccups or a movement while falling asleep. Other types are abnormal. The condition can be classified according to:

  • Underlying cause
  • Pattern of movement
  • Origin within the body

The movements are caused by an abnormal electrical discharge in the nervous system. The electrical discharge may begin in the:

  • Brain
  • Spinal cord
  • Nerves in the body

The message travels along the nerves to the muscle. The nerve stimulates a muscle or group of muscles to suddenly contract.

The Nervous System Pathways
CNS and PNS
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What triggers the abnormal electrical discharge depends on the cause. Myoclonus is often a symptom of a nervous system or metabolic condition. Possible causes include: