High rates of periodic leg movements of sleep in REM-sleep behavior disorder raise more questions about the relationship between sleep-related movement disorders: Article reviewed: M.L. Fantini, M. Michaud, N. Gosselin, G. Lavigne, J. Montplaisir, Periodic leg movements in REM sleep behavior disorder and related autonomic and EEG activation, Neurology, 59 (2002) 1889–1894

Abstract

Objectives: Assess prevalence of periodic leg movements (PLMs) of sleep and the association of heart rate changes to these leg movements, in patients with REM behavior disorder (RBD) compared to patients with the restless legs syndrome (RLS). Study design: Case series. Study population: Forty consecutive patients with RBD and 15 patients with RLS. Methods: Polysomnography was performed in patients with RBD (without RLS) and a (presumably) historical age and gender-matched group with primary RLS. Of the 28 RBD patients with a PLM index greater than 10/h, 15 were randomly selected for further analysis of leg movement characteristics and consequences, and again compared to the RLS group. No patients in either group were taking medications known to affect sleep. Scoring of REM was performed without the EMG channel. Fifty leg movements from Stage II sleep were randomly selected for each patient. Change in heart rate from baseline for the 10 beats before, and 15 beats after, each leg movement onset was determined, and averaged within groups. Results: Seventy percent of patients with RBD had a PLM index greater than 10/h. Mean PLM index was no different between the RBD and RLS groups for wake or non-REM, though it was higher for the RBD group during REM sleep. Cardiac acceleration following PLM onset in the RBD group was over twice that seen in the RLS group, even though a smaller percentage of leg movements was associated with cortical arousal in those with RBD. Conclusions: PLM indices are the same in RBD and RLS, further supporting the dopaminergic hypothesis for generation or control of periodic leg movements during sleep (PLMS). PLMS are more common in RBD during REM sleep than observed in RLS. Reduced autonomic activation associated with leg movements in RBD may be related to idiopathic RBD or to a neurodegenerative disorder underlying the RBD. Similarly, the lack of cortical arousal seen with PLMS in RBD may indicate dysregulation of centers responsible for coordinating autonomic and cerebral activity during sleep.