Defining morphology of periodic leg movements in sleep: an evidence-based definition of a minimum window of sustained activity
- 117 Downloads
Current standard guidelines for scoring periodic leg movements (PLM) define the start and end of a movement but fail to explicitly specify the movement morphology necessary to classify an EMG event as a PLM, rather than some other muscle event. This is currently left to the expert visual scorer to determine. This study aimed to define this morphology to provide a consistent standard for visual scoring and to improve automatic periodic leg movements in sleep scoring.
A review of expert PLM scoring produced a hypothesized morphology criterion: a window of high EMG activity within the movement lasting at least 0.5 s. Two diverse expert visual scorers were independently presented with images of EMG tracings from candidate leg movements (CLM) that either passed or failed this requirement (aka “full” or “empty” movements, respectively), and indicated whether each should be scored as CLM. The 0.5-s window was compared with alternatives of 0.25 and 0.75 windows.
Expert scorers on average identified 94 % of “full” movements as CLM in contrast to only 8.5 % of “empty” movements. The proposed minimum window of 0.5 s also resulted in the highest agreement between visual scorers and between scorers and an automatic program.
An added criterion requiring 0.5 s of high EMG activity within a valid CLM improves the accuracy of automatic scoring algorithms in relation to the gold standard of expert visual scorers. Our results suggest that this rule is an accurate representation of the morphology feature used by experts. This new rule has the potential to improve consistency and accuracy of visual and automatic scoring of PLM.
KeywordsPLMS Morphology Automatic scoring Electromyography
Sleep data acquisition and scoring were provided by The Center for Interdisciplinary Sleep Research and Education (CISRE) at Johns Hopkins University.
Compliance with ethical standards
This study was supported in part by a grant from the National Institute for Neurological Diseases and Stroke number NS075184. The sponsor had no role in the design or conduct of this research.
Conflict of interest
All authors certify that they have no affiliations with or involvement in any organization or entity with any financial interest (such as honoraria; educational grants; participation in speakers bureaus; membership, employment, consultancies, stock ownership, or other equity interest; and expert testimony or patent-licensing arrangements), or non-financial interest (such as personal or professional relationships, affiliations, knowledge or beliefs) in the subject matter or materials discussed in this manuscript.
All procedures performed in studies involving human participants were in accordance with the ethical standards of the institutional and/or national research committee and with the 1964 Helsinki declaration and its later amendments or comparable ethical standards.
Informed consent was obtained from all individual participants included in the study.
- 5.Zucconi M, Ferri R, Allen R, et al. (2006) The official World Association of Sleep Medicine (WASM) standards for recording and scoring periodic leg movements in sleep (PLMS) and wakefulness (PLMW) developed in collaboration with a task force from the International Restless Legs Syndrome Study Group. Sleep Med 7:175–183. doi: 10.1016/j.sleep.2006.01.001 CrossRefPubMedGoogle Scholar
- 8.Berry R, Brooks R, Gamaldo C, et al (2015) The AASM Manual for the Scoring of Sleep and Associated Events. Rules, Terminology and Technical Specifications, Version 2.2. Darien, ILGoogle Scholar
- 10.Huang AS, Skeba P, Yang MS, et al (2015) MATPLM1, A MATLAB script for scoring of periodic limb movements: preliminary validation with visual scoring. Sleep Med. doi: 10.1016/j.sleep.2015.03.008
- 11.Frauscher B, Kunz A, Brandauer E, et al (2011) Fragmentary myoclonus in sleep revisited: a polysomnographic study in patients. Sleep Med 12:410–5. doi: 10.1016/j.sleep.2010.08.016Google Scholar