Sleep related rhythmic movement disorder revisited.

To classify sleep related rhythmic movement disorder (SRMD) based on clinical, polysomnographic and videometric evaluation in a predominantly adult population, twenty-four patients (four females) aged 11-67 years identified by polysomnography and videometry were classified for type of SRMD, its duration and frequency during wakefulness and in the different sleep stages. SRMD persisted unto child- and adulthood in all patients. SRMD is not restricted to sleep-wake transition, occurs most frequently in wake, stages NREM 1 and 2, but also in REM and slow wave sleep. Most patients have one form of SRMD, few have two forms in one night. Longest duration is in wakefulness. Duration does not differ from one sleep cycle to another. Sleep is not fragmented by SRMD, and sleep stages generally do not change when SRMD occurs. Only few patients have short awakenings after SRMD. In four patients with sleep apnea SRMD coincided frequently with the onset of the apnea related arousal. Two patients had a family history of SRMD. In contrast to the ICSD-2 SRMD seems to persist into adulthood frequently with male preponderance. Familial forms are rare. SRMD in the investigated population is always occurring during sleep, even if patients reported it to occur strictly at wake-sleep transition. Polysomnography is a useful method to uncover SRMD aggravated by other sleep disorders and allows insight in some aspects of the pathology of this disorder, which is not well understood. In the adult patients it is not associated with mental pathologies and can be triggered by sleep apnea.