Study of neck myoclonus isolated and associated to other involuntary movements during the sleep

Abstract

Introduction We assessed the frequency and characteristics of neck myoclonus during sleep in a prospective sleep- disorder cohort, and investigated its correlates and associations with other involuntary movements. Materials and methods We studied 51 consecutive patients with parasomnia or hipersomnia (37 men; mean age 54 ± 18) undergoing routine time-synchronized videopolysomnography at the sleep laboratory. Neck myoclonus was defined as sudden, non-sustained dorsal or ventral flexion or version of the head to one side with varying amplitude from mild to intense. We differentiated between isolated neck myoclonus and that associated to other involuntary movements in the limbs or body. We excluded neck movements preceded by arousals, positional change, apnea o periodic legs movements. Results Ninety-six per cent of the patients had at least one neck myoclonus during sleep. The mean number of neck myoclonus was 1.18/h sleep (IC 95%: 0.65 ∼ 1.72). Movements were more frequent during REM sleep than NREM (1.16 and 0.36 respectively, p: 0.016). Isolated and associated neck myoclonus occurred with similar frequency (isolated 4.0 ± 5.7 and associated 4.7 ± 7.1). About half of the neck myoclonic movements were accompanied by simultaneous movements of other body parts, predominantly in the arms (mean 1.8 ± 2.5), and approximately 50% of them induced an arousal. The number of patients was too small to establish a study by ages. Conclusion In the sleep laboratory neck myoclonus is observed in most patients but it occurs occasionally, most of then in REM sleep. Isolated neck myocloni are as frequent as neck myocloni associated with other movements in the body, especially arm movements. Acknowledgements We thank Dr. Joan Santamaria for his scientific supervission.