Myoclonus is an uncontrollable, brief and rapid twitching of a muscle or muscle groups.

Some types of myoclonus 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

You may be at risk for myoclonus if you have a family history of the disorder. 


An abnormal electrical discharge in the nervous system causes these movements. The message travels along the nerves to the muscle. The nerve stimulates a muscle or group of muscles to suddenly contract.

The electrical discharge may begin in the:

  • Brain
  • Spinal cord

Myoclonus is often a symptom of a nervous system or metabolic condition. Possible causes include:

  • A lack of oxygen or nutrients
  • Certain medications or toxins
  • Nervous system disorders, such as:
    • Head or spinal cord trauma or injury
    • Tumors of the brain or spinal cord
    • Multiple sclerosis
    • Parkinson's disease
    • Alzheimer's disease
    • Creutzfeldt-Jakob disease and other prion diseases
    • Huntington's disease
    • Encephalitis
    • Stroke
    • Epilepsy
    • Coma
    • Paraneoplastic syndromes
  • Metabolic disorders, such as:
    • Lipid storage disease
    • Electrolyte imbalance
    • Respiratory failure
    • Liver failure
    • Kidney failure


Myoclonic symptoms vary from mild to severe. The sudden jerking or twitching may occur once in a while or often and may be limited to one region of the body or affect all muscle groups.

Light, sound, touch or movement may be triggers. Movements can occur at rest or during other movements. There may be one or a series of twitches. Sometimes, the jerking occurs in a pattern. Myoclonus can become so severe that it interferes with eating, speaking or walking.


Your doctor will determine the following:

  • The localization of the myoclonus in the nervous system
  • If an underlying condition is responsible for the symptoms

Your doctor may measure your brain activity. This can be done with an electroencephalogram (EEG).

Your doctor may also take pictures of your brain and spinal cord. This can be done with:

  • MRI scan
  • CT scan


Initial treatment tries to cure any underlying causes, such as tumors or electrolyte imbalances. If these treatments don’t work, then treatment aims to reduce how severe the movements are. You may need multiple medications to reduce twitching. Some may have serious side effects.

Content was created using EBSCO’s Health Library. Edits to original content made by Rector and Visitors of the University of Virginia. This information is not a substitute for professional medical advice.