History and terminology The term myoclonus was derived from the longer term paramyoklonus multiplex that was first used in a case report by professor Nikolaus Friedreich in Heidelberg in 1881 with the intent to describe symmetric (para) and quick (clonus) movements of muscles (myo) occurring in multiple sites (multiplex) over the body. Lowenfeld, in 1883, was the first to use the term myoclonus by shortening paramyoklonus multiplex, as quoted by Seelingmüller in 1886. Myoclonus is a clinical sign encompassing a vast range of etiologies, anatomical sources, and pathophysiological features. Muscle jerks can also be produced by the spinal cord where the motor system is organized on two levels, spinal and propriospinal. The spinal segmental system may became hyperexcitable, and the result is spinal “segmental” myoclonus involving one or two contiguous spinal myotomes that is particularly resistant to supraspinal influences, such as voluntary movement, mental activity and sleep. The propriospinal system is a slowly conducting intraspinal pathway that connects multiple segmental levels. Involvement of this system leads to predominantly axial jerks that, unlike spinal segmental myoclonus, is particularly influenced by mental activity and sleep.Bussel et al., in 1988, described a patient in whom rhythmic extension movements of the trunk and lower limbs started 15 months after a traumatic section of the spinal cord, verified by MRI, at the lower cervical cord. The timing of the muscle activation in different muscles remained “fixed,” but was not measured.
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