title: A Data-Driven Analysis of the Rules Defining Bilateral Leg Movements during Sleep.
abstract: OBJECTIVE
  The aim of this study was to describe and analyze the association between bilateral leg movements (LMs) during sleep in subjects with restless legs syndrome (RLS), in order to eventually support or challenge the current scoring rules defining bilateral LMs.
  
  
  METHODS
  Polysomnographic recordings of 100 untreated patients with RLS (57 women and 43 males, mean age 57 y) were included. In each recording, we selected as reference all LMs that occurred during sleep and that were separated from another ipsilateral LM by at least 10 sec of EMG inactivity. For each reference LM and an evaluation interval from 5 sec before the onset to 5 sec after the offset of the reference LM, we evaluated (1) the presence or absence of contralateral leg movement activity and (2) the distribution of the onset-to-onset and (3) the offset-to-onset differences between bilateral LMs.
  
  
  RESULTS
  We selected a mean of 368 (± 222 standard deviation [SD]) reference LMs per subject. For 42% (± 22%) of the reference LMs no contralateral leg movement activity was observed within the evaluation interval. In 55% (± 22%) exactly one and in 3% (± 2%) more than one contralateral LM was observed. A further evaluation of events where exactly one contralateral LM was observed showed that in most (1) the two LMs were overlapping (93% ± 9% SD) and (2) were classified as bilateral according to the World Association of Sleep Medicine and the International Restless Legs Syndrome Study Group (WASM/ IRLSSG) (96% ± 6% SD) and (3) the American Academy of Sleep Medicine scoring rules (99% ± 2% SD). Although there was a systematic and statistically significant difference in standard LM indices during sleep based on the two different definitions of bilateral LMs, the size of the difference was not clinically meaningful (maximum individual, absolute difference in LM indices ± 2.5). In addition, we found that the duration of LMs within bilateral LM pairs was longer compared to monolateral LMs and that the duration of the single LMs in bilateral LM pairs tended to correlate.
  
  
  CONCLUSIONS
  The results of this study indicate that the two current standard scoring rules for the definition of bilateral LMs during sleep provide largely corresponding classifications in subjects with RLS and, in a clinical context, can be considered to be equivalent.
authors.affiliation: Sleep Research Centre, Department of Neurology IC, Oasi Institute for Research on Mental Retardation and Brain Aging (IRCCS), Troina, Italy.
authors.forename: Raffaele
authors.initials: R
authors.lastname: Ferri
authors.affiliation: Sleep and Epilepsy Center, Neurocenter of Southern Switzerland, Civic Hospital (EOC) of Lugano, Lugano, Switzerland.
authors.forename: Mauro
authors.initials: M
authors.lastname: Manconi
authors.affiliation: Sleep Research Centre, Department of Neurology IC, Oasi Institute for Research on Mental Retardation and Brain Aging (IRCCS), Troina, Italy.
authors.forename: Francesco
authors.initials: F
authors.lastname: Rundo
authors.affiliation: Sleep and Epilepsy Center, Neurocenter of Southern Switzerland, Civic Hospital (EOC) of Lugano, Lugano, Switzerland.
authors.forename: Marco
authors.initials: M
authors.lastname: Zucconi
authors.affiliation: Sleep Research Centre, Department of Neurology IC, Oasi Institute for Research on Mental Retardation and Brain Aging (IRCCS), Troina, Italy.
authors.forename: Debora
authors.initials: D
authors.lastname: Aricò
authors.affiliation: Department of Social and Developmental Psychology, Sapienza University, Rome, Italy.
authors.forename: Oliviero
authors.initials: O
authors.lastname: Bruni
authors.affiliation: Sleep Disorders Center, Department of Neurology, Scientific Institute and University Ospedale San Raffaele, Vita-Salute University, Milan, Italy.
authors.forename: Luigi
authors.initials: L
authors.lastname: Ferini-Strambi
authors.affiliation: Sleep and Epilepsy Center, Neurocenter of Southern Switzerland, Civic Hospital (EOC) of Lugano, Lugano, Switzerland.
authors.forename: Stephany
authors.initials: S
authors.lastname: Fulda
mesh_terms: D005260:Female; D006801:Humans; D007866:Leg / Q000503:physiopathology*; D008297:Male; D008875:Middle Aged; D009068:Movement; D017286:Polysomnography; D012148:Restless Legs Syndrome / Q000175:diagnosis / Q000503:physiopathology*; D012189:Retrospective Studies; D012890:Sleep / Q000502:physiology*; D056508:Sleep Medicine Specialty
keywords: PLMS; bilateral leg movements; periodic leg movements during sleep; restless legs syndrome; sleep scoring