Periodic Limb Movements during Sleep Mimicking REM Sleep Behavior Disorder.

STUDY OBJECTIVE To describe a group of patients referredbecause of abnormal sleep behaviors that were suggestive ofREM sleep behavior disorder (RBD) in whom videopolysomnographyruled out RBD and showed the reportedbehaviors associated with vigorous periodic limb movementsduring sleep (PLMS). METHODS Clinical history and video-polysomnography reviewof patients identified during routine visits in a sleepcenter. RESULTS Patients were fifteen men and two women with a median age of 66 (range 48-77) years. Reported sleep behaviors were kicking (n=17), punching (n=16), gesticulating (n=8), falling out of bed (n=5), assaulting the bed partner (n=2), talking (n=15) and shouting (n=10). Behaviors resulted in injuries in three bed partners and one patient. Twelve (70.6%) patients were not aware of displaying abnormal sleep behaviors that were only noticed by their bed partners. Ten (58.8%) patients recalled unpleasant dreams such as being attacked or chased. Video polysomnography showed 1) frequent and vigorous stereo typed PLMS involving the lower limbs, upper limbs and trunk (median PLMS index 61.2; median PLMS index in NREM sleep 61.9; during REM sleep only eight patients had PLMS and Gaig et al. -4- their median PLMS index in REM sleep was 39.5), 2) abnormal behaviors (e.g., punching, groaning) during some of the arousals that immediately followed PLMS in NREM sleep, and3) ruled out RBD and other sleep disorders such as obstructive sleep apnea. Dopaminergic agents were prescribed in fourteen out of the seventeen patients andresulted in improvement of abnormal sleep behaviors and unpleasant dreams in all of them. After dopaminergictreatment, follow-up video-polysomnography in seven patients showed a decrease in the median PLMS index from baseline (108.9 vs 19.2, p=0.002) and absence of abnormal behaviors during the arousals. CONCLUSIONS Abnormal sleep behaviors and unpleasant dreams simulating RBD symptomatology may occur in patients with severe PLMS. In these cases, video-polysomnography rulesout RBD and identifies prominent PLMS followed by arousals containing abnormal behaviors. Our cases represent an objectively documented subtype of periodic limb movement disorder causing abnormal sleep behaviors.