Myoclonus is a brief and rapid twitching of a muscle or group of muscles. It cannot be stopped or controlled.
There are many types. Some are normal, like hiccups. Other types are not normal, such as a reaction to a medicine.
The movements are caused by an unusual electrical signal in the nervous system. It starts in the brain, spinal cord, or nerves and travels to a muscle. It may be caused by:
- A lack of oxygen or nutrients
- Certain medicines or toxins
- Problems of the nervous system
- Metabolic disorders
- Damage to the brain or spinal column
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This problem is more common in people who have other family members with myoclonus. Other things that may raise the risk are:
Injuries or illness of the brain and spinal cord, such as:
- Head or spinal cord trauma or injury
- Tumors of the brain or spinal cord
- Multiple sclerosis
- Parkinson disease
- Alzheimer disease
- Creutzfeldt-Jakob disease and other prion diseases
- Huntington disease
- Paraneoplastic syndromes—problems that happen in people with certain types of cancer
- Metabolic disorders, such as:
Problems vary from person to person. A person will have jerking, twitching, or spasms that:
- Range from mild to severe
- Happen every once in a while or often
- Affect one area of the body or the entire body
- Happen at rest or during other movements
Mild forms may be a twitch followed by release, such as hiccups. Moderate forms may cause a shock-like spasm in muscle groups. Severe forms can make it hard to eat, speak, or walk.
The doctor will ask about your symptoms and health history. A physical exam will be done. Myoclonus is a symptom not a disease. This is often enough to make the diagnosis.
Tests may be done to look for a cause. These may be:
Treatment will focus on the cause. The goal is to manage symptoms.
Medicine that is causing myoclonus may be stopped or changed. Medicine may also be needed to reduce twitching. One of more of these may be used:
- Antiseizure medicine
- Dietary supplements
- Adrenocorticotropic hormone (ACTH)
Prevention will depend on the cause.
National Institute of Neurological Disorders and Stroke
Canadian Association of Neuroscience Nurses
Eberhardt O, Topka H. Myoclonic disorders. Brain Sci. 2017;7(8):E103.
Michaeil-Demo Y, Gavvala JR, et al. Clinical classification of post anoxic myoclonic status. Resuscitation. 2017;119:76-80.
Myoclonus—approach to the patient. EBSCO DynaMed website. Available at:https://www.dynamed.com/approach-to/myoclonus-approach-to-the-patient. Accessed October 6, 2020.
Last reviewed September 2020 by EBSCO Medical Review Board Rimas Lukas, MD Last Updated: 5/21/2021