Myoclonus
Definition
Myoclonus is a brief, rapid, shock-like jerking movement.
Description
Myoclonus can be a symptom of a separate disorder, or can be the only or primary neurological finding, in which case it is termed "essential myoclonus." Myoclonus may occur in epilepsy, or following many different types of brain injury, such as lack of oxygen, stroke, trauma, or poisoning. Myoclonus can occur in one or more limbs, or may be generalized, involving much of the body.
Demographics
Because myoclonus is so often part of another disorder, the prevalence of myoclonus is not known with certainty. One study indicates that the prevalence of all types of myoclonus may be approximately 10 per 100,000 population.
Causes and symptoms
Myoclonus can be a symptom of a very wide variety of disorders. A partial list includes:
- epilepsy (several types)
- Tay-Sachs disease and other storage diseases
- spinocerebellar degenerative diseases
- Hallervorden-Spatz syndrome
- Huntington's disease
- multiple system atrophy
- corticobasal degeneration
- Creutzfeldt-Jakob disease
- brain infections, including HIV
- focal brain damage, including from stroke or tumor
- heat stroke
- electrical shock
- hypoxia (oxygen deprivation)
- toxins and drugs
Myoclonus also occurs normally, as a person falls asleep or while sleeping. This type of myoclonus is not associated with disease.
Diagnosis
The diagnosis of myoclonus is not difficult, and depends on careful patient description of the symptoms. Much more effort is devoted to determining the underlying cause. Blood tests, neuroimaging studies, genetic tests, electroencephalography (EEG) and other types of studies may be performed in order to determine the underlying disorder.
Treatment team
Myoclonus is treated by a neurologist.
Treatment
If an underlying disorder can be identified, this is treated with the expectation that successful treatment may diminish the myoclonus. In many cases this is not possible, however. Alternatively, the underlying disorder may
Several medications can be used to reduce the severity or frequency of the myoclonus. Valproic acid and clonazepam are the two most widely used drugs. Anticholinergic drugs, such as benztropine or trihexyphenidyl, may be useful. Anticonvulsants may be helpful, as may benzodiazepines, depending on the type of myoclonus. Deep brain stimulation has been reported to help at least one patient. Botulinum toxin injection may be useful in focal myoclonus.
