Prague Med. Rep. 2017, 118, 5-13

Excessive Fragmentary Myoclonus: What Do We Know?

Jiří Nepožitek, Karel Šonka

Centre for Sleep and Wake Disorders, Department of Neurology, First Faculty of Medicine, Charles University and General University Hospital in Prague, Prague, Czech Republic

Received November 6, 2016
Accepted March 9, 2017

Excessive fragmentary myoclonus (EFM) is a polysomnographic finding registered by the surface electromyography (EMG) and characterized as a result of the muscle activity consisting of sudden, isolated, arrhythmic, asynchronous and asymmetric brief twitches. The EMG potentials are defined by the exact criteria in The International Classification of the Sleep Disorders, 3rd edition and they appear with high intensity in all sleep stages. Clinical significance of EFM is unclear. It was observed in combination with other diseases and features such as obstructive and central sleep apnea, narcolepsy, periodic limb movements, insomnia, neurodegenerative disorders and peripheral nerve dysfunction. Relation to such wide range of diseases supports the opinion that EFM is nor a specific sleep disorder nor a specific polysomnographic sign. The option that EFM is a normal variant has also not been ruled out so far.


This study was supported by a grant by the Ministry of Health of the Czech Republic, GIGH-16-28914A and a grant by Charles University, GAUK 64216.


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