brain, spinal cord, and nerve disorders
Myoclonus
Introduction
Myoclonus refers to quick, lightning-like jerks (contractions) of a muscle or a group of muscles. Myoclonus may occur normally (for example, jerking of a leg when a person is falling asleep), but it may result from a disorder, such as liver failure, a head injury, low blood sugar, or Parkinson disease or from use of certain drugs. Muscles may jerk quickly or slowly, and jerking may be rhythmic or not. Doctors diagnose myoclonus based on symptoms and do blood tests, electromyography, and/or magnetic resonance imaging to identify the cause. The cause of myoclonus is corrected if possible, but if the cause cannot be corrected, certainorclonazepam(a mild sedative) may lessen symptoms. (See also Overview of Movement Disorders .) Myoclonus may involve only one hand, a group of muscles in the upper arm or leg, or a group of facial muscles. Or it may involve many muscles at the same time. Myoclonus may be classified in many different ways: By cause: Whether it occurs normally, is caused by a disorder or drug, or has no identifiable cause By severity: How much of the brain is damaged or how severe the symptoms are By location: Where the brain is damaged By triggers: Whether it is triggered by a stimulus (such as bright light or a sudden noise) or occurs on its own (spontaneously) Classifying the type of myoclonus may help doctors identify the cause and choose appropriate treatments. 