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 (IRLSSG)

Single leg movement during which the EMG drops below the offset criteria for less than 0.5s. Abbreviations: EOG-R, EOG-L, right and left electrooculogram, respectively; F3-A2, C3-A2, O1-A2, electroencephalogram from 3 different left scalp locations referred to the right earlobe; Chin, electromyogram of the submentalis muscle; ECG, electrocardiogram; Airflow, oronasal airflow by thermistors; Thorax and Abdomen, chest wall and abdominal movements by strain gauges, respectively; Tib-R and Tib-L, right and left anterior tibialis muscle electromyogram, respectively.

Sequence of PLM, two of which show a duration longer than 5s (arrows). Abbreviations as in Fig. 1.

Two examples of movements occurring on the two sides considered as bilateral because they are overlapping or separated (offset-to-onset) by less than 0.5s. Abbreviations as in Fig. 1.

Overview of the detection parameters for candidate PLM.

Sequence of leg movements overlapping with or occurring within ±0.5s of breathing resumption of sleep apnea events (vertical dashed lines). Abbreviations as in Fig. 1.

Example of missing PLM (arrows). Note the presence of short bursts of delta waves (A1 CAP subtypes) approximately where the missing PLM were expected to occur. Abbreviations as in Fig. 1.

Anterior tibialis EMG and rectified leg activity data for PLM events. The middle line is a marker showing the detection of the prior event as meeting criteria for PLM. Note the remarkable similarity in duration and morphology of the activity meter and the EMG.

Example of association of PLM with arousal. Note the different extension of the same EEG event if considered as an ASDA arousal or CAP A3 subtype. Abbreviations as in Fig. 1.