Heart rate change and clinical characteristics in patients with neck myoclonus: An observational study

OBJECTIVE: This study was conducted to evaluate heart rate (HR) change and clinical characteristics in patients with neck myoclonus (NM), a physiological motor phenomenon occurring during sleep. METHODS: For 18 consecutive patients in whom NM was confirmed from video-polysomnography, we analyzed 576 NMs. Change rate of HR at each 1 sec point towards the averaged HR in prior 5 sec period was calculated before and after all NM events. RESULTS: Findings show NM events as more prevalent during REM sleep than during NREM sleep (83.9% vs. 16.1%). For NM without cortical arousal in REM and NREM sleep, the respective HR increased 20 s before NM (p < 0.05); the change rate was up to 13%. For NM with cortical arousal in REM sleep, the HR increased 50 s before NM (p < 0.05); the change rate reached 18%. Three NM subjects showed abnormal vocalization or shouting during REM. Six NM subjects had excessive daytime sleepiness without sleep disorder. CONCLUSION: HR increased before NM events, which may be associated with pathophysiology of NM. NM may possibly be associated with excessive daytime sleepiness or abnormal behaviors during REM sleep. SIGNIFICANCE: HR increase is associated with pathophysiology of NM and clinical symptoms.