Pediatric Movement Disorders

Pediatric Movement Disorders - Myoclonus

Description

Myoclonus is "sudden, brief, jerky, shock-like, involuntary movements" (Fahn et al. 1986). The movements are quite rapid and may be triggered by attempts at voluntary movement, sensory stimulation, or startle. Myoclonus may cause rhythmic jerks, in which case, it is termed a "myoclonic tremor." Myoclonus is categorized based upon the likely source of movement. Such sources include cortical or subcortical areas or the spinal cord.

Cortical myoclonus is thought to be due to a lack of inhibition in the sensory or motor cortex. Subcortical myoclonus is often due to abnormalities in the brainstem; spinal myoclonus is presumed to be due to abnormalities in spinal inhibitory circuits. Myoclonus may be severely disabling, particularly when it is triggered by movement. In some cases, it may also be very mild. The most common example of a mild myoclonus is sleep myoclonus. In this form of myoclonus, children or adults have occasional brief jerks of an arm or a leg; these "jerks" occur while the individual is falling asleep. Negative myoclonus is a sudden involuntary relaxation of a muscle, rather than a contraction; this is thought to be due to mechanisms similar to those of sleep myoclonus. Cortical reflex myoclonus is triggered by attempts to obtain a knee jerk or other tendon reflex. Epilepsia partialis continua is a type of focal epilepsy that causes myoclonic tremor. Myoclonus is often associated with epilepsy; there is a particular class of degenerative disorders called "progressive myoclonus epilepsies (PME)" in which the association of myoclonus and epilepsy is common.

Please see the following topics related to myoclonus below, and available on the left side of this page.

WE MOVE makes every effort to present medical information that is up-to-date and accurate. The material provided has undergone rigorous medical review. Information regarding the authors, editors, publisher, and medical reviewers of this material of the WE MOVE Web site is listed below.

Medical science is constantly changing. Therefore, the authors, editors, and publisher do not warrant that the information in this text is complete, nor are they responsible for omissions or errors in the text or for the results of the use of this information. This information does not replace consultation with a physician. All medical procedures, drug doses, indications, and contraindications should be discussed with your personal physician.

Section Author: Terence Sanger, MD PhD
Scientific Reviewers: Leon Dure, MD, Associate Professor of Pediatrics and Neurology, The University of Alabama at Birmingham; Marjorie A Garvey, MD, Pediatrics and Developmental Neuropsychiatry Branch, NIMH, Human Motor Control Section, NINDS; Jonathan W. Mink, MD PhD, Associate Professor of Neurology, Neurobiology & Anatomy, and Pediatrics Chief, Child Neurology, University of Rochester Medical Center, Rochester, New York
Editor: Joy B. Leffler, NASW, AMIA