title: A descriptive analysis of neck myoclonus during routine polysomnography.
abstract: OBJECTIVE
  Although episodes of neck myoclonus (head jerks) in REM sleep have a characteristic appearance, they have so far not been described systematically in video-polysomnography. This study assesses the occurrence, frequency, and characteristics of neck myoclonus in REM sleep in a prospective sleep disorder cohort, and investigates clinical correlates and associations with medication.
  
  
  METHODS
  University hospital sleep disorders center.
  
  
  METHODS
  Two-hundred twenty-eight mixed sleep disorder patients.
  
  
  METHODS
  Not applicable.
  
  
  RESULTS
  REM sleep was screened visually for short "stripe-shaped" movement-induced artifacts visible vertically over the EEG leads in polysomnographic registration. If such artifact was present, the synchronized video was inspected for the presence of neck myoclonus. Out of 205 patients, 54.6% (n = 112) had neck myoclonus during REM sleep. The mean neck myoclonus index was 1.0 +/- 2.7/h REM sleep. Younger patients had a higher neck myoclonus index than older patients (< 45 years versus 45-60 years versus > 60 years: 1.8 +/- 4.2 versus 0.6 +/- 1.1 versus 0.5 +/- 1.1; P = 0.004). Ninety-five percent of subjects < 45 years had a neck myoclonus index between 0 and 9.4/h; 95% of subjects > 45 years had a neck myoclonus index between 0 and 2.7/h. Patients on benzodiazepine treatment had no neck myoclonus (0/112 vs. 13/93; P < 0.001). In 23 patients, additional surface neck EMG was performed. EMG activation associated with neck myoclonus had a mean duration of 0.6 +/- 0.4 sec. Correlation between duration of neck EMG activation and movement-induced EEG artifact duration was very high (rho = 0.96; P < 0.001).
  
  
  CONCLUSIONS
  Neck myoclonus is common during REM sleep and more frequent in younger individuals. This could indicate that neck myoclonus during REM sleep is a physiological phenomenon. If there is a cut-off distinguishing normal from excessive has to be investigated in further studies.
authors.affiliation: Department of Neurology, Innsbruck Medical University, Innsbruck, Austria. birgit.ho@i-med.ac.at
authors.forename: Birgit
authors.initials: B
authors.lastname: Frauscher
authors.forename: Elisabeth
authors.initials: E
authors.lastname: Brandauer
authors.forename: Viola
authors.initials: V
authors.lastname: Gschliesser
authors.forename: Tina
authors.initials: T
authors.lastname: Falkenstetter
authors.forename: Martin T
authors.initials: MT
authors.lastname: Furtner
authors.forename: Hanno
authors.initials: H
authors.lastname: Ulmer
authors.forename: Werner
authors.initials: W
authors.lastname: Poewe
authors.forename: Birgit
authors.initials: B
authors.lastname: Högl
mesh_terms: D000293:Adolescent; D000328:Adult; D000367:Age Factors; D000368:Aged; D000369:Aged, 80 and over; D016477:Artifacts; D015331:Cohort Studies; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D009207:Myoclonus / Q000175:diagnosis / Q000503:physiopathology*; D009334:Neck Muscles / Q000503:physiopathology*; D017286:Polysomnography; D012893:Sleep Wake Disorders / Q000175:diagnosis / Q000503:physiopathology; D012895:Sleep, REM / Q000502:physiology; D014741:Video Recording; D055815:Young Adult
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