Elsevier

The Lancet Neurology

Volume 3, Issue 10, October 2004, Pages 598-607
The Lancet Neurology

Review
Myoclonus: current concepts and recent advances

https://doi.org/10.1016/S1474-4422(04)00880-4Get rights and content

Summary

Myoclonus presents as a sudden brief jerk caused by involuntary muscle activity. An organisational framework is crucial for determining the medical significance of the myoclonus as well as for its treatment. Clinical presentations of myoclonus are divided into physiological, essential, epileptic, and symptomatic. Most causes of myoclonus are symptomatic and include posthypoxia, toxic-metabolic disorders, reactions to drugs, storage disease, and neurodegenerative disorders. The assessment of myoclonus includes an initial screening for those causes that are common or easily corrected. If needed, further testing may include clinical neurophysiological techniques, enzyme activities, tissue biopsy, and genetic testing. The motor cortex is the most commonly shown myoclonus source, but origins from subcortical areas, brainstem, spinal, and peripheral nervous system also occur. If treatment of the underlying disorder is not possible, treatment of symptoms is worthwhile, although limited by side-effects and a lack of controlled evidence.

Section snippets

Epidemiology

Only a few large inclusive clinical series have been reported. Among these series, the demographics and relative proportions of different diagnostic categories varies substantially.3 Even so, these studies show that symptomatic (secondary) causes of myoclonus are most common, epileptic seizures and myoclonus are intertwined, and essential (primary and non-progressive) myoclonus only constitutes a small proportion of patients with myoclonus. The only epidemiological study on myoclonus due to any

Clinical presentation and aetiology

The best possible clinical presentations of myoclonus are best organised by use of the major clinical syndrome categories of Marsden and colleagues1 and their corresponding lists of known causes (panel 1). The myoclonus presenting from the causes under a given category will share syndrome properties corresponding to that category. However, the same category may contain forms of myoclonus with various physiological properties. Furthermore, the same causal factor may produce vastly different

Assessment and clinical neurophysiology

The guidelines for the assessment of a patient with myoclonus may be broken up into four parts (panel 3).

Pathophysiology

Results from clinical neurophysiology testing give important insight into the generation of the myoclonus. However, other considerations should be realised about the pathophysiology of myoclonus. The clinical features of myoclonus are largely determined by the nature of the affected motor systems. Thus, cortical myoclonus predominantly affects those body parts with the biggest cortical representations, the hands and face, and, as the motor areas of the cerebral cortex are most involved in

Treatment

The best strategy for the treatment of myoclonus is, of course, the treatment of the underlying disorder. Some causes of myoclonus can be reversed partially or totally, such as an acquired abnormal metabolic state, a medication or toxin, or an excisable lesion. There is some evidence that psychogenic jerks respond to psychotherapy and pharmacological psychiatric treatment.50, 59 However, in most myoclonus cases, such treatment of the underlying disorder is not possible. Ideally, an approach to

Conclusion

Myoclonus has seen tremendous progress in recent years with regard to description of myoclonus syndromes, clinical neurophysiology, and pathophysiology. Despite this progress, this disabling movement disorder still awaits more major advances before better treatments are more widely available. Physicians desperately need treatments specifically designed for myoclonus rather than those intended for other disorders. Further discovery of genetic mutations will yield more specific information with

Search strategy and selection criteria

References for this review were identified by searches of MEDLINE between January 1, 1996 and April 1, 2004 and references from relevant articles; numerous articles were also identified through searches of the extensive files of the authors. The search terms “myoclonus”, “myoclonic epilepsy”, “myoclonic seizures”, “treatment”, “piracetam”, “levetiracetam”, “diagnosis”, “therapy” were used. Abstracts and reports from meetings were also included. Only papers published in English were

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