Excessive Fragmentary Myoclonus: Time of Night and Sleep Stage Distributions

Abstract

Excessive fragmentary myoclonus during sleep consists of high amounts of brief twitch-like movements occurring asynchronously and asymmetrically in different body areas and has been reported to occur in association with a number of sleep disorders. It was analyzed using a new technique of quantification, the fragmentary myoclonus index (FMI). The FMI exhibited high rates in all stages of sleep but with a somewhat lower frequency in slow wave sleep explaining, as well, a significantly lower rate in the first hour after sleep onset compared to later hours. There was no evidence for greater sleep fragmentation or lighter sleep compared to a matched patient group in whom it had not been noted. RESUME: Myoclonic fragmentaire excessive: horaire nocturne et stades du sommeil. La myoclonic fragmentaire excessive pendant le sommeil consiste en un nombre considerable de mouvements fasciculaires se produisant de facjon asynchrone et symetrique dans differentes regions du corps. Ce phenomene a ete rapporte en association avec un grand nombre de troubles du sommeil. Nous l'avons analyse au moyen d'une nouvelle technique de quantification, l'indice de myoclonie fragmentaire (IMF). L'IMF etait eleve dans tous les stades du sommeil, avec une tendance vers des frequences moins elevees pendant le sommeil a ondes lentes, ce qui explique egalement des frequences significativement plus basses dans la premiere heure apres l'endormissement par rapport aux heures suivantes. II n'existait pas d'evidence de fragmentation du sommeil ou de sommeil plus leger compare a un groupe de patients apparies, chez qui ce phenomene n'avait pas ete note.Can. J. Neurol. Sci. 1993; 20: 142-146 Physiological fragmentary myoclonus occurring in normal human subjects was first described by De Lisi 1 as consisting of brief, fine, twitch-like movements involving various body areas in asynchronous and asymmetric fashion and observable at sleep onset and at times during sleep. Using surface EMG electrodes, normal fragmentary myoclonus has been recorded as muscle potentials of 50-200 ^tV in amplitude and less than 150 msec in duration most prominent in the distal limbs and facial areas and predominating during REM sleep and at sleep onset. 2 -3 Fragmentary myoclonus (FM) must be distinguished from the normal phenomenon of so-called sleep starts or hypnic jerks, which also occur at sleep onset, but consist of bilaterally synchronous gross body movements. 4 -5 It also differs from several pathological forms of sleep-related myoclonus. Epileptic myoclonus can occur during sleep and is associated with a EEG discharge. 6 Periodic limb movement disorder 7 -8 is easily distinguished by the more sustained nature and pseudorhythmic repetition of the jerks.Excessively intense and frequent FM has been reported to occur in association with a variety of clinical diagnoses, almost always in males and in combination with high amounts of sleep fragmentation. 9 It has also been reported in patients in whom excessive daytime sleepiness (EDS) was the sole complaint ...

Excessive Fragmentary Myoclonus: What Do We Know?

“…has not yet been confirmed in EFM (Lins et al, 1993). Occurrence of EFM in wakefulness is not quite clear.…”

“…It can be summarized that the highest EFM amounts occur in R and the lowest in N3 (Lins et al, 1993;Mizuma and Sakamoto, 1997), while the abnormal intensity in contrast with PFM, is kept. In the recent work by Hoque et al (2013) the sleep stage distribution was assessed for the different amplitude criteria.…”

“…The time of night distribution has been studied as well, the number of potentials rise sharply after the initial lower level in the first hour of sleep and remains unchanged across the rest of the night (Lins et al, 1993).…”

“…Thus this count led to the number ranging from 0 to 10 for each 30-second epoch. The count then could be referenced to the hours of night and to the duration of individual sleep stages (Lins et al, 1993).…”

“…Epileptic myoclonus as an expression of epilepsy in sleep is always associated with an EEG discharge (Lins et al, 1993).…”