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Demystifying the spontaneous phenomena of motor hyperexcitability

Research output: Contribution to journalReview articlepeer-review

Original languageEnglish
Pages (from-to)1830-1844
Number of pages15
JournalClinical Neurophysiology
Issue number8
Accepted/In press29 Mar 2021
PublishedAug 2021

Bibliographical note

Funding Information: JB acknowledges funding from the Medical Research Council and Motor Neurone Disease Assocation (Lady Edith Wolfson Clinical Research Training Fellowship; MR/P000983/1), Sattaripour Charitable Foundation and UK Dementia Research Institute. WKC contributed during his MSc qualification in Clinical Neuroscience. EC received funding through a clinical fellowship from the MRC Centre for Neurodevelopmental disorders. Publisher Copyright: © 2021 International Federation of Clinical Neurophysiology Copyright: Copyright 2021 Elsevier B.V., All rights reserved.

King's Authors


Possessing a discrete functional repertoire, the anterior horn cell can be in one of two electrophysiological states: on or off. Usually under tight regulatory control by the central nervous system, a hierarchical network of these specialist neurons ensures muscular strength is coordinated, gradated and adaptable. However, spontaneous activation of these cells and their axons can result in abnormal muscular twitching. The muscular twitch is the common building block of several distinct clinical patterns, namely fasciculation, myokymia and neuromyotonia. When attempting to distinguish these entities electromyographically, their unique temporal and morphological profiles must be appreciated. Detection and quantification of burst duration, firing frequency, multiplet patterns and amplitude are informative. A common feature is their persistence during sleep. In this review, we explain the accepted terminology used to describe the spontaneous phenomena of motor hyperexcitability, highlighting potential pitfalls amidst a bemusing and complex collection of overlapping terms. We outline the relevance of these findings within the context of disease, principally amyotrophic lateral sclerosis, Isaacs syndrome and Morvan syndrome. In addition, we highlight the use of high-density surface electromyography, suggesting that more widespread use of this non-invasive technique is likely to provide an enhanced understanding of these motor hyperexcitability syndromes.

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