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Myoclonus

Definition

Myoclonus is a brief and rapid twitching of a muscle or group of muscles. The twitching happens quickly. It can’t be stopped or controlled.

There are many types of myoclonus. Some are normal, like the hiccups or moving while falling asleep. Other types are not normal. They are classified based on the:

  • Cause
  • Pattern of movement
  • Origin within the body

Causes    TOP

An unusual electrical discharge in the nervous system causes the movements. The electrical discharge may start in the:

  • Brain
  • Spinal cord
  • Nerves in the body

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

The Nervous System Pathways

CNS and PNS
Copyright © Nucleus Medical Media, Inc.

What triggers the discharge depends on the cause. Myoclonus is often a symptom of a nervous system or metabolic problem. Possible causes are:

Risk Factors    TOP

You have an increased risk if you have family members who have had myoclonus.

Symptoms    TOP

Myoclonic symptoms range from mild to severe. This depends on the cause of the problem. It may start when you are a child or an adult. The sudden jerking or twitching may be once in a while or often. It may affect one region of the body or all muscle groups.

Light, sound, touch, or movement may be triggers. Or, it may happen for no known reason. Movements can occur at rest or during other movements. There may be one or a series of twitches. Sometimes, the jerking happens in a pattern. Other times, there is no pattern. Myoclonus can become so severe that it gets in the way of eating, speaking, or walking.

Diagnosis    TOP

You will be asked about your symptoms and health history. A physical exam will be done.

Your bodily fluids may be tested. This can be done with blood tests.

You may have your brain and muscle activity measured and recorded. This can be done with:

Pictures may be taken of your brain and spinal cord. This can be done with:

Treatment    TOP

Treatment will start by attempting to cure any causes, such as tumors or electrolyte imbalances. If this doesn’t work, then treatment aims to reduce how severe the movements are. In some case, many drugs are needed to reduce twitching. Some have serious side effects.

Here are some medicines:

  • Sedatives
  • Anticonvulsants
  • Dietary supplements
  • Adrenocorticotropic hormone (ACTH)

Prevention    TOP

Taking these steps may help to lower your chance of myoclonus:

  • Take care to prevent brain injury. For example, wear a helmet when riding a bike or motorcycle.
  • If twitching starts after you begin a new medicine, tell your doctor. Your doctor may be able to lower the dose or advise a different medicine.

RESOURCES:

National Institute of Neurological Disorders and Stroke
http://www.ninds.nih.gov

CANADIAN RESOURCES:

Canadian Association of Neuroscience Nurses
http://cann.ca

References:

Dalmau J, Rosenfeld MR. Paraneoplastic syndromes of the CNS. Lancet Neurology. 2008;7:327-340.
Eberhardt O, Topka H. Myoclonic disorders. Brain Sci. 2017;7(8):E103.
Michaeil-Demo Y, Gavvala JR, Bellinski IL, et al. Clinical classification of post anoxic myoclonic status. Resuscitation. 2017;119:76-80.
Myoclonus and its disorders. Neurologic Clinics. August 2001.
Last reviewed June 2018 by EBSCO Medical Review Board Rimas Lukas, MD
Last Updated: 6/12/2018

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