What are the key features of periodic limb movement disorder (PLMD)?
Periodic limb movements, formerly called nocturnal myoclonus , are characterized on PSG by frequent clusters of extremity movements (typically the legs, but occasionally the arms) that tend to recur periodically during sleep at intervals of 5 to 90 seconds.
The frequency is >15/hr in adults and >5/hr in children.
When these events produce arousals, as they often do, the sleep pattern may be severely disrupted, and the patient may experience significant daytime sleepiness.
When there is clinical sleep disturbance or daytime impairment in conjunction with the PSG findings of periodic limb movements, then a diagnosis of PLMD can be made.
PLMD is thought to be rare as periodic limb movements are typically associated with restless legs syndrome (RLS), RBD, or narcolepsy and represent a distinct diagnosis from PLMD.
