Overview

Myoclonus refers to a quick jerking movement that you can't control. Hiccups are a form of myoclonus, as are the sudden jerks or "sleep starts" that you may feel just before falling asleep. These forms of myoclonus occur in healthy people and usually aren't serious.

Other forms of myoclonus may occur because of a nervous system disorder, such as epilepsy, a metabolic condition, or a reaction to a medicine.

Treating whatever condition causes myoclonus can help control symptoms. Sometimes the cause of myoclonus is unknown or can't be specifically treated. In these cases, the goal of treatment is to reduce the effects of myoclonus on quality of life.

Symptoms

People with myoclonus often describe their symptoms as jerks, shakes or spasms that are:

  • Sudden
  • Brief
  • Involuntary
  • Shock-like
  • Variable in intensity and frequency
  • Occurring in one part of the body or all over the body
  • Sometimes severe enough to interfere with eating, speaking or walking

When to see a doctor

If your myoclonus symptoms become frequent and persistent, talk to your health care provider about a diagnosis and treatment options.

Causes

Myoclonus may be caused by a variety of underlying problems. It is commonly separated into different types based on what is causing it. The cause can help determine treatment.

Physiological myoclonus

This type of myoclonus occurs in healthy people and rarely needs treatment. Examples include:

  • Hiccups.
  • Sleep starts.
  • Shakes or spasms due to anxiety or exercise.
  • Infant muscle twitching during sleep or after a feeding.

Essential myoclonus

Essential myoclonus occurs on its own, usually without other symptoms and without being related to any underlying illness. The cause of essential myoclonus is often unknown. In some cases, the cause is hereditary, meaning passed down in families.

Epileptic myoclonus

This type of myoclonus occurs as part of an epileptic disorder.

Symptomatic myoclonus

Symptomatic myoclonus results from an underlying medical condition. It is sometimes called secondary myoclonus. Examples include:

  • Head or spinal cord injury.
  • Infection.
  • Kidney or liver failure.
  • Lipid storage disease.
  • Chemical or drug poisoning.
  • Prolonged oxygen deprivation.
  • Medicine reaction.
  • Autoimmune inflammatory conditions.
  • Metabolic disorders.
  • Coronavirus disease 2019 (COVID-19).

Nervous system conditions that result in secondary myoclonus include:

  • Stroke.
  • Brain tumor.
  • Huntington's disease.
  • Creutzfeldt-Jakob disease.
  • Alzheimer's disease.
  • Parkinson's disease and Lewy body dementia.
  • Corticobasal degeneration.
  • Frontotemporal dementia.
  • Multiple system atrophy.
By Mayo Clinic Staff