Motor disturbances during non-REM and REM sleep in narcolepsy-cataplexy: a video-polysomnographic analysis

Motor events during sleep can be frequently observed in patients with narcolepsy-cataplexy. We hypothesized that increased motor events and related arousals contribute to sleep fragmentation in this disease. We aimed to perform a detailed whole-night video-polysomnographic analysis of all motor events during non-rapid eye movement and rapid eye movement sleep in a group of narcolepsy-cataplexy patients and matched controls, and to assess the association with arousals. Video-polysomnographic registrations of six narcolepsy-cataplexy patients and six sex- and age-matched controls were analysed. Each motor event in the video was classified according to topography, number of involved body parts, duration and its association with arousals. The mean motor activity index was 59.9 ± 23.0 h(-1) in patients with narcolepsy-cataplexy compared with 15.4 ± 9.2 h(-1) in controls (P = 0.004). Distribution of motor events was similar in non-rapid eye movement and rapid eye movement sleep in the patient group (P = 0.219). In narcolepsy-cataplexy, motor events involved significantly more body parts (≥ 2 body regions: 38.2 ± 15.6 versus 14.9 ± 10.0; P = 0.011). In addition, the proportion of motor events lasting longer than 1 s was higher in patients than controls (88% versus 44.4%; P < 0.001). Both total and motor activity-related arousal indices were increased in narcolepsy-cataplexy (total arousal index: 21.6 ± 9.0 versus 8.7 ± 3.5; P = 0.004; motor activity-related arousal index: 17.6 ± 9.8 versus 5.9 ± 2.3; P = 0.002). Motor activity and motor activity-related arousal indices are increased in both non-rapid eye movement and rapid eye movement sleep in narcolepsy-cataplexy compared with controls. This supports the concept of a general sleep motor dysregulation in narcolepsy-cataplexy, which potentially contributes to or even underlies sleep fragmentation in this disease.