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. 2011 Apr;12(4):410-5.
doi: 10.1016/j.sleep.2010.08.016.

Fragmentary Myoclonus in Sleep Revisited: A Polysomnographic Study in 62 Patients


Fragmentary Myoclonus in Sleep Revisited: A Polysomnographic Study in 62 Patients

Birgit Frauscher et al. Sleep Med. .


Study objectives: To investigate the frequency of fragmentary myoclonus (FM) in a sleep-disorder population, to analyze its distribution across sleep stages and to examine potential associations with clinical correlates and night-to-night variability.

Design: Retrospective review of 102 polysomnographic records.

Setting: Sleep laboratory at a University Hospital Neurology Department.

Patients: Sixty-two sleep-disorder patients.

Interventions: None.

Measurements and results: Fragmentary myoclonus (FM) was counted according to published criteria. Sleep stage specific FM indices (FMI) were calculated for each patient. Median FMI was 39.5/h sleep. FMI was the highest in REM sleep, followed by similar indices in wakefulness, S1 and S2 sleep, and was the lowest in S3/S4 sleep (n.s.). FMI increased with age (ρ=0.350, P=0.005). Men had a higher FMI than women (median 55.8/h vs. 24.1/h, P=0.042). In addition, FMI was positively correlated with the presence of sleep-related breathing disorders (ρ=0.270, P=0.036), respiratory indices (apnea-hypopnea index: ρ=0.403, P=0.002; oxygen desaturation index: ρ=0.378, P=0.004) and body mass index (ρ=0.28, P=0.028). In a linear regression model, age, male sex and oxygen desaturation index were significant (P<0.05). FMI night-to-night variability was 1.6 (range: 1.0-3.9).

Conclusion: Fragmentary myoclonus was present in every patient of this sleep-disorder population. Its clinical significance is unknown, but the association with oxygen desaturation index points to an association with sleep-related breathing disorders. Since FMI was similar during wakefulness and light sleep, these data challenge the concept of a primarily sleep-related phenomenon.

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