Sleep-related myoclonus in rheumatic pain modulation disorder (fibrositis syndrome) and in excessive daytime somnolence.

We describe a new syndrome, Rheumatic Pain Modulation Disorder (RPMD) ("fibrositis syndrome") with sleep-related myoclonus (involuntary periodic leg movements). Measures of sleepiness, fatigue and pain, before and after sleep, and aspects of sleep of nine subjects (Ss) with RPMD and sleep-related myoclonus were compared to nine subjects with excessive daytime somnolence and sleep-related myoclonus. In eight of the RPMD with sleep-related myoclonus and three of those with daytime sleepiness, an alpha (7.5-11 Hz) EEG Non-Rapid Eye Movement sleep disorder was demonstrated. The RPMD with sleep-related myoclonus group contained a greater number of women, more pain, morning fatigue, and disturbances in sleep (more stage changes and alpha EEG sleep prior to leg myoclonus); but in comparison to the sleep-related myoclonus, daytime somnolent group, there were no differences in evening and morning sleepiness, number of limb movements, movement arousals, awakenings after sleep onset, sleep duration, and percent sleep stages.