Fragmentary myoclonus in idiopathic rapid eye movement sleep behaviour disorder

Abstract

Summary Fragmentary myoclonus is a result of muscle activity consisting of brief potentials in surface electromyography during polysomnography. Excessive fragmentary myoclonus is defined by increased intensity of the potentials. A few studies report excessive fragmentary myoclonus occurrence in neurodegenerative diseases. Because idiopathic rapid eye movement sleep behaviour disorder is considered as an early stage of neurodegeneration with involvement of the brainstem, we charted the prevalence and quantified the intensity of excessive fragmentary myoclonus in idiopathic rapid eye movement sleep behaviour disorder. Twenty‐nine patients (one woman, 28 men, mean age 68 years, SD 6.2) and 29 controls (two women, 27 men, mean age 65.6 years, SD 8.6) underwent polysomnography. Fragmentary myoclonus potentials were identified and counted according to internationally used criteria. Fragmentary myoclonus intensity was quantified by the fragmentary myoclonus index. Excessive fragmentary myoclonus was diagnosed in 75.9% (22 subjects) in idiopathic rapid eye movement sleep behaviour disorder, while in 34.5% (10 subjects) among the controls (p = 0.003). Quantitative analysis showed a wide‐range fragmentary myoclonus index in idiopathic rapid eye movement sleep behaviour disorder (4.0–632.4; median 60.7) and in the controls (0.8–938.1; median 34.3). The overall difference in fragmentary myoclonus index was not significant between the groups; however, patients with idiopathic rapid eye movement sleep behaviour disorder showed trends for higher fragmentary myoclonus index scores in wakefulness (p = 0.027), N1 (p = 0.032), N3 (p = 0.046) and R (p = 0.007). Fragmentary myoclonus index does not correlate with age, idiopathic rapid eye movement sleep behaviour disorder duration or R stage atonia deficiency. The prevalence of excessive fragmentary myoclonus is higher in idiopathic rapid eye movement sleep behaviour disorder compared with the controls, so fragmentary myoclonus should be taken into account in future research of rapid eye movement sleep behaviour disorder and motor control in sleep.

Sleep in Parkinson’s disease

“…Due to the multifactorial aspects of sleep disorders in patients with PD, vPSG will often provide much more detailed, objective, and quantifiable information about the underlying aspects of the sleep disorder in an individual patient, and at the same time provide information about sleep integrity or fragmentation, the number of arousals or awakenings, the total sleep efficiency, respiration during sleep and respiratory events, and the quantification of motor activity during sleep, ranging from REM sleep without atonia (RWA)/RBD to PLM, fragmentary myoclonus [72,134] and others. vPSG in patients with PD should in every case include not only the usual EMG channels of mental/ submental muscles and tibial anterior muscles, but also of upper extremity muscles (flexor digitorum superficialis from both arms).…”

Non-REM sleep with hypertonia in Parkinsonian Spectrum Disorders: A pilot investigation

“…While the networks involved in NRH manifestation are yet to be determined, concomitant motor activity during wake, NREM and REM sleep, could provide further clarification especially in those with a PSD [ 35 ]. Distributions of NRH in the PD group relative to DLB/PDD were similar to those previously observed for RSWA [ 14 ].…”

A reliable automatic algorithm to score fragmentary myoclonus

“…Lins et al introduced the FM index, quantifying FM frequency (Lins et al, 1993). Patients with idiopathic RBD and sleep disorder patients showed a wide range of FM index (Frauscher et al, 2011; Nepozitek et al, 2019). All previous works employed manual scoring for FM index quantification.…”

“…The presence of FM was investigated in 100 healthy sleepers, and EFM criteria were fulfilled in nine subjects (Frauscher et al, 2014). Previous studies reported the association of EFM with peripheral nerve injury (Raccagni et al, 2016), sleep related respiratory disturbances (Broughton et al, 1985), rapid eye movement (REM) sleep behaviour disorder (RBD) (Nepozitek et al, 2019) and Parkinson's disease (Sobreira-Neto et al, 2015), and of FM index with the oxygen desaturation index (Frauscher et al, 2011). Lins et al introduced the FM index, quantifying FM frequency (Lins et al, 1993).…”

“…Dashed red lines show the threshold of 20 minutes of NREM sleep with EFM. EFM, excessive fragmentary myoclonus; NREM, non rapid eye movement; ρ, correlation coefficient and related p-value ( p-val) et al, 2011;Frauscher et al, 2014;Nepozitek et al, 2019). The reason for the higher FM indices in W and REM could be the higher muscular tone in W and the muscle twitches typical of REM sleep.…”