Myoclonus
From Freepedia
Myoclonus is 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. Contractions are called positive myoclonus; relaxations are called negative myoclonus. The most common time for people to encounter them is while falling asleep ("sleep starts") but myoclonic jerks are also a symptom of a number of neurological disorders. Hiccups are also a kind of myoclonic jerk specifically affecting the diaphragm.
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.
Anatomically, myoclonus may originate from lesions of the cortex, subcortex or spinal cord. The presence of myoclonus above the foramen magnum effectively excludes spinal myoclonus, but further localisation relies on further investigation with electromyography (EMG) and electroencephalography (EEG).
Familiar examples of normal myoclonus include hiccups and hypnic jerks 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.
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Is there any treatment?
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.
What is the prognosis?
Although myoclonus is not a life-threatening condition, it may result in serious, debilitating impairments.
What research is being done?
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.
External links
- The first version of this article was adapted from the public domain NINDS Myoclonus Information Page. Please amend and adapt as needed.
- What is a myoclonic jerk?
- Falling-Asleep Twitches
Reference
- Myoclonus Fact Sheet, National Institute of Neurological Disorders and Stroke (viewed 5 Apr 2005)
