Neurophysiologie clinique = Clinical neurophysiology
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Myoclonus is a movement disorder characterized by the occurrence of an involuntary abrupt muscle contraction causing a sudden unexpected jerk. Many other movement disorders can present with the same jerky, shock-like appearance. This paper reviews the clinical and neurophysiologic arguments supporting the distinction between true myoclonus and various imitators, including chorea, ballism, tics, dystonia, stereotypy, tremor and restless limbs. To be differentiated from myoclonus, these movement disorders, despite their heterogeneity, are distinctive through the patterned profile of muscle activation, the longer duration of the muscle contraction, the conditions in which they occur, and their suppressibility at will.
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A huge number of neurological disorders are associated with myoclonus. This paper describes these disorders whose diagnosis partly relies on the presence of myoclonus. The diagnostic approach is related to certain clinical features of myoclonus, which, after their integration in the clinical context, help orientate towards diagnosis. ⋯ Myoclonus with focal neurological signs may be observed in thalamic lesions, responsible for unilateral asterixis or unilateral myoclonus superimposed on dystonic posture. Segmental spinal myoclonus or propriospinal myoclonus may be associated with several spinal-cord disorders. Myoclonus associated with peripheral nerve lesions is exceptional or even questionable for some of these.