Excessive fragmentary myoclonus in NREM sleep: a report of 38 cases.

We report 38 consecutive patients referred to a sleep disorder clinic who on diagnostic polysomnography showed excessive amounts of brief fragmentary myoclonus throughout all stages of NREM sleep. Almost all patients were male despite a reasonably equal sex distribution of referral. The phenomenon was found associated with sleep-related respiratory problems, periodic movements in sleep (PMS), narcolepsy, intermittent hypersomnia and (rarely) insomnia. It also occurred associated with excessive daytime sleepiness (EDS) as an isolated polysomnographic finding apart from some degree of sleep fragmentation.