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)

The definition and scoring criteria for periodic leg movements (PLM) during sleep have not changed since 1990 and 1993 and are substantially based on the work carried out by Coleman et al. in 1982. The aim of the Atlas and Scoring Rules was to provide recommendations for the correct recording of motor events, the use of standard terminology and the definition of some common rules to quantify PLM. However, the current standard for recording sleep is based on computerized technology, and new pathologies have been recognized to be associated with PLM during sleep (PLMS), different motor patterns have also been detected and new sophisticated methods of signal analysis have changed our understanding of the impact of PLM on sleep patterns. In particular, the analysis of the electromyogram (EMG) signal and of the periodicity of the phenomenon provides different methods for the evaluation of muscle activity in normal and pathological sleep. Even small changes in the criteria of detection of the single PLM may have a significant impact on the final results of the analysis by altering the range of the PLM included. This could significantly modify the numerous characteristics derived from analyses of the PLM. Moreover, changes in the classification criteria of events, inter-movement intervals and periodicity can influence significantly the indexes related to PLM, thereby impacting the evaluation of sleep disorders. The Task Force of PLM Scoring of the International Restless Legs Syndrome Study Group (IRLSSG) wishes to define innovative strategies to evaluate, count and score leg movements during sleep and wakefulness, which respond both to the new requirements of computerized sleep recording and also to the developing understanding of the different pathologies presenting with PLM. These new guidelines apply to adults; they are expected to be valid also for children, but are recommended for cautious use with children pending further pediatric evaluations of PLM.