Myoclonus is a brief and rapid twitching of a muscle or muscle groups. The twitching happens suddenly. It cannot be stopped or controlled.
There are different types of myoclonus. Some occur normally, like the hiccups or a movement while falling asleep. Other types are abnormal. The condition can be classified according to:
- Underlying cause
- Pattern of movement
- Origin within the body
The movements are caused by an abnormal electrical discharge in the nervous system. The electrical discharge may begin in the:
- Spinal cord
- Nerves in the body
The message travels along the nerves to the muscle. The nerve stimulates a muscle or group of muscles to suddenly contract.
The Nervous System Pathways
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What triggers the abnormal electrical discharge depends on the cause. Myoclonus is often a symptom of a nervous system or metabolic condition. Possible causes include:
- A lack of oxygen or nutrients
- Certain medications or toxins
Nervous system disorders, such as:
- Head or spinal cord trauma or injury
- Tumors of the brain or spinal cord
- Multiple sclerosis
- Parkinson's disease
- Alzheimer's disease
- Creutzfeldt-Jakob disease and other prion diseases
- Huntington's disease
- Paraneoplastic syndromes—disorders that happen in people with certain types of cancer
- Metabolic disorders, such as:
Last reviewedJuly 2013by Rimas Lukas, MD; Michael Woods, MD
Please be aware that this information is provided to supplement the care provided by your physician. It is neither intended nor implied to be a substitute for professional medical advice. CALL YOUR HEALTHCARE PROVIDER IMMEDIATELY IF YOU THINK YOU MAY HAVE A MEDICAL EMERGENCY. Always seek the advice of your physician or other qualified health provider prior to starting any new treatment or with any questions you may have regarding a medical condition.