The level of observed physical movement accompanying periodic limb movements measured in a clinical sleep population

Abstract

Study objectives: Periodic limb movements (PLMs) are routinely measured during polysomnogram (PSG) testing. During the early years of sleep testing, physical movements were identified and over time, consensus ultimately led to the current definitions of movement disorders including criteria used to measure PLMs on PSG testing. There has been considerable debate about the clinical importance of the PLMs measured during PSG testing. Over the last decade, the author has observed significant variations in the actual visible physical movements observed with a PLM event. This report is the result of work to quantify the amount of movement and the frequency of movements observed among individuals who have PLMs. Methods/principal findings: Consecutive PSGs performed in a suburban sleep center for an initial diagnosis of a sleep disorder were retrospectively reviewed to identify those with measured PLMs. Of 646 studies on patients >18 years, 460 met criteria for inclusion. Visual assessment of movements was carried out on all of those with PLM events measured using American Academy of Sleep Medicine guidelines. The movements were quantified based on the number of extremities observed to move. PLMs were observed in 237 of the 460 studies that met inclusion criteria (52%). As expected, the PLMs occurred more frequently in older individuals. PLMs occurred with equal frequency in both sexes. Apnea occurred with equal frequency in those with and without observed physical movements. Of those with PLMs, 62% (147) demonstrated observable physical movements. Significant movements involving three or four extremities occurred in 16% of individuals with PLMs. No physical movements were observed in 38%. Conclusion: In this uncontrolled, nonrandom, observational series, visual physical movements with a PLM event identify a unique subset of individuals with PLMs. The presence of any visual movements or more pronounced visual movements involving multiple extremities may represent markers for PLM disorder, for clinically significant PLMs with other disorders, or for other clinical conditions or physiologic variables.