What is Nocturnal Myoclonus?
Nocturnal myoclonus, also known as periodic limb movement disorder or PLMD, is a form of myoclonus in which the symptoms of the disorder are experienced during sleep. Myoclonus is itself a disease symptom, rather than a diagnosis, which manifests as sudden muscular contractions or muscular relaxation. Muscular contraction or relaxation can occur in response to a trigger, or may occur randomly. Occasional involuntary muscle twitches and hiccups are examples of non-disordered myoclonus. Many people who experience nocturnal myoclonus do not have accompanying negative side effects. They may simply move their limbs during sleep without being disturbed by the movement. In these cases the person is said to have periodic limb movements during sleep, or PLMS. This is not the same as PLMD, as PLMS is not a disorder in itself, and does not always require treatment. PLMS is, however, a symptom of PLMD.
