Study objectives: To evaluate the type, duration, and distribution of rhythmic movements in sleep stages in school-aged children and young adults; to find out if cases of rhythmic movement disorder persisting beyond infancy are associated with any daytime symptoms or psychopathology.
Design: All participants underwent neurologic examination, biochemical screening, electroencephalography, neuroimaging, overnight videopolysomnography, and psychologic examination.
Setting: Department of Neurology and Sleep Laboratory, 1st Medical Faculty, Charles University, Prague.
Patients or participants: Ten subjects referred to the sleep disorders center because of rhythmic movement disorder. Five males, 5 females; age range, 7-24 years; mean age 14.7 +/- 5.69 years.
Interventions: None.
Measurements and results: Biochemical screening, electroencephalogram, and neuroimaging were unremarkable in all cases. According to duration, 2 types of rhythmic movements were observed on polysomnography: longer episodes appeared in wakefulness and in non-rapid eye movement stage 1 sleep, while shorter episodes (2-80 seconds) occurred during non-rapid eye movement stage 2, non-rapid eye movement stage 3-4, and rapid eye movement sleep. According to sleep-stage distribution, we defined (a) rhythmic movements prevailing in the first half of the night and in the morning hours, usually associated with wakefulness or superficial sleep; (b) rhythmic movements occurring throughout the night in all sleep stages; (c) rhythmic movements prevailing in the second half of the night and mainly associated with rapid eye movement sleep. Psychologic examination showed symptoms of the attention-deficit/hyperactivity disorder in 6 cases.
Conclusions: According to our study, rhythmic movement disorder persisting beyond infancy may be connected with various daytime symptoms; a strong association between rhythmic movement disorder and attention-deficit/hyperactivity disorder was found in school-aged children. We speculate that pathogenetic mechanisms similar to those in attention-deficit/hyperactivity disorder are involved in rhythmic movement disorder or that symptoms of attention-deficit/hyperactivity disorder may be secondary to rhythmic movement disorder.