Overview

Myoclonus refers to a quick, involuntary muscle jerk. Hiccups are a form of myoclonus, as are the sudden jerks, or "sleep starts," you may feel just before falling asleep. These forms of myoclonus occur in healthy people and rarely present a problem.

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

Ideally, treating the underlying cause will help control your myoclonus symptoms. If the cause of myoclonus is unknown or can't be specifically treated, then treatment focuses on reducing the effects of myoclonus on your quality of life.

Myoclonus care at Mayo Clinic

Symptoms

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

  • Sudden
  • Brief
  • Involuntary
  • Shock-like
  • Variable in intensity and frequency
  • Localized to 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 doctor for further evaluation and proper diagnosis and treatment.

Causes

Myoclonus may be caused by a variety of underlying problems. Doctors often separate the types of myoclonus based on their causes, which helps determine treatment. Types of myoclonus include the following categories.

Physiological myoclonus

This type of myoclonus occurs in normal, 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 unexplained (idiopathic) or, in some cases, hereditary.

Epileptic myoclonus

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

Symptomatic (secondary) myoclonus

Muscle jerks that occur as a result of an underlying medical condition, including:

  • Head or spinal cord injury
  • Infection
  • Kidney or liver failure
  • Lipid storage disease
  • Chemical or drug poisoning
  • Prolonged oxygen deprivation
  • Medication reaction
  • Autoimmune inflammatory conditions
  • Metabolic disorders

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