Myoclonus is a term that refers to brief, involuntary twitching of a muscle or a group of muscles. It describes a symptom and, generally, is not a diagnosis of a disease. The myoclonic twitches or jerks are usually caused by sudden muscle contractions; they also can result from brief lapses of contraction. Myoclonic jerks may occur alone or in sequence, in a pattern or without pattern. They may occur infrequently or many times each minute. Most often myoclonus is one of several symptoms in a wide variety of nervous system disorders such as multiple sclerosis, Parkinson’s disease, Alzheimer’s disease, or Creutzfeldt-Jakob disease. Familiar examples of normal myoclonus include hiccups, and jerks or "sleep starts" that some people experience while drifting off to sleep. Severe cases of pathologic myoclonus can distort movement and severely limit a person’s ability to eat, talk, and walk. Myoclonic jerks commonly occur in individuals with epilepsy. The most common types of myoclonus include action, cortical reflex, essential, palatal, progressive myoclonus epilepsy, reticular reflex, sleep, and stimulus-sensitive.
Treatment for myoclonus consists of medications that may help reduce symptoms. Many of these drugs, which include barbiturates, clonazepam, phenytoin, primidone, and sodium valproate, are also used to treat epilepsy. The complex origins of myoclonus may require the use of multiple drugs for effective treatment.
Although myoclonus is not a life-threatening condition, it may result in serious, debilitating impairments.
Current research is attempting to clarify and expand the knowledge about myoclonus. Scientists are seeking to understand the biochemical basis of involuntary movements and to find the most effective treatment for myoclonus and other movement disorders.