Periodic limb movement disorder

Periodic limb movement disorder (PLMD), also known as nocturnal myoclonus or periodic movements in sleep, is a disorder of intermittent movements of the extremities during sleep. It usually affects the legs, but occasionally the arms. The movements are periodic, highly stereotypical, and may or may not be associated with arousals from sleep. As PLMD frequently causes sleep fragmentation and consequently nocturnal insomnia, we also discuss it in Chapter 8. When it exists without arousals or sleepiness, however, it may be classified under undesired movements during sleep (see Chapter 8).