Definition

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.

Causes

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

The Nervous System Pathways

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Risk Factors

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
  • Encephalitis
  • Stroke
  • Epilepsy
  • Coma
  • Paraneoplastic syndromes—problems that happen in people with certain types of cancer
• Metabolic disorders, such as:
  • Lipid storage disease—a problem that is found at birth
  • Electrolyte imbalance
  • Respiratory failure
  • Liver failure
  • Kidney failure
  • Malabsorption syndromes, such as Whipple disease or celiac disease

Symptoms

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.

Diagnosis

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:

• Blood and urine tests
• Electroencephalogram (EEG) to check the electrical activity in the brain
• Electromyogram (EMG) to check the electrical activity in the muscles
• MRI scan to look at structures in the brain or spine

Treatment

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:

• Sedatives
• Antiseizure medicine
• Dietary supplements
• Adrenocorticotropic hormone (ACTH)

Prevention

Prevention will depend on the cause.