Periodic leg movements during sleep: phenotype, neurophysiology, and clinical significance

• Periodic leg movements during sleep are an objective finding in restless legs syndrome.
• Sleep periodic leg movements have a typical phenotype that enables their identification.
• A genetic background underlies periodic leg movements during sleep.
• PLMS have significant clinical correlates, including cardiovascular disease.
• Specific aspects in children require special attention in this age group.

Periodic leg movements during sleep (PLMS) are the most important objective finding in restless legs syndrome (RLS). During the last decade, PLMS have been very important for the assessment and comprehension of their pathophysiological correlates, which have been paralleled by the emergence of new computer-assisted and data-driven rules for their identification, scoring, and analysis. The present article focused on the most relevant PLMS-related findings of the last decade, and sought to provide a coherent and comprehensive overview on this enigmatic motor phenomenon. First, a clear description was made on the identification, quantification, and scoring of PLMS and their associated events. This was followed by a description of the current knowledge of their neurophysiologic aspects. Then, the typical phenotype of genuine PLMS in RLS and other clinical conditions was described, allowing for their careful separation from other sleep leg motor activities. In addition, the most recent findings on the genetics of PLMS were briefly summarized, followed by the current evidence on their clinical correlates, which is another rapidly advancing field of research. The description of the specific aspects of PLMS in children was also carefully reported, with important clues on their evaluation in this age group. Finally, further research was proposed, which may lead to consideration of PLMS as a clinically significant concern, independent of the association with RLS.