EEG and cardiac activation during periodic leg movements in sleep - Support for a hierarchy of arousal responses

Objective: To investigate other physiologic changes that occur with periodi c leg movements during sleep (PLMS) that might be considered to be more sen sitive indices of sleep fragmentation. Background: Although PLMS are associ ated with recurrent microarousals (MA), the frequency of PLMS with MA does not correlate with objective daytime sleepiness. It is postulated that the lack of correlation results from the low sensitivity of the standard criter ia used to score MA. Methods: Ten drug-free patients with a polygraphic and clinical diagnosis of restless legs syndrome (RLS) and PLMS were examined. The EEG correlates of PLMS were analyzed by visual scoring and spectral an alysis during PLMS that ended in a visible microarousal (PLMS with MA) or n ot (PLMS without MA). The R-R interval in the EKG signal was also examined. Results: A total of 34% of PLMS were associated with MA lasting >3 seconds , and 3% of PLMS were associated with MA lasting <3 seconds. Although PLMS with MA were associated with an increase in alpha activity, for PLMS withou t MA a significant increase in delta and theta activity was present. Both t ypes of PLMS induced a shortening of the R-R interval; this was particularl y more marked for PLMS with MA. Conclusions: First, visual scoring of MA. t hat include a duration of less than 3 seconds has little effect on the dete ction of PLMS with MA. Second, EEG activation and tachycardia are present d uring both types of PLMS. Third, a hierarchy in the arousal response is pre sent-going from autonomic activation to bursts of delta activity to alpha a ctivity to a full awakening.