[The classification of myoclonus]

The term "myoclonus" was originally used to indicate brief jerky involuntary movements. But, nowadays the meaning of myoclonus has expanded so much that its definition and classification have been considerably obscured. In this view, the definition of myoclonus is described and the characteristic clinical features are discussed. The classification of myoclonus is presented based on the pathophysiological observations. Myoclonus is divided into two large groups, cortical myoclonus directly associated with the activity of the motor cortex, and subcortical myoclonus which comprises various types of myoclonus (including spinal myoclonus). Furthermore, the electrophysiological aspects of myoclonus and its pathogenesis are briefly discussed.