Periodic limb movement disorder

Periodic limb movement disorder
Specialty	Neurology

Periodic limb movement disorder (PLMD) is a sleep disorder where the patient moves limbs involuntarily and periodically during sleep, and has symptoms or problems related to the movement. PLMD should not be confused with restless legs syndrome (RLS), which is characterized by a voluntary response to an urge to move legs due to discomfort. PLMD on the other hand is involuntary, and the patient is often unaware of these movements altogether. Periodic limb movements (PLMs) occurring during daytime period can be found but are considered as a symptom of RLS; only PLMs during sleep can suggest a diagnosis of PLMD.^[1]

Periodic limb movement disorder is characterized by recurrent episodes of frequent limb movements while sleeping. It mostly happens in the lower parts of the body like the toes, ankles, knees and hips. It can also, in some cases, appear in the upper extremities of the body. These movements can lead the patient to wake up, and if so, sleep interruption can be the origin of excessive daytime sleepiness.^[2]

PLMD is characterized by increased periodic limb movements during sleep, which must coexist with a sleep disturbance or other functional impairment, in an explicit cause-effect relationship.^[3][4] Usually, these involuntary movements come from lower extremities (including toes, ankles, knees, and hips), although they can also be observed in upper extremities, occasionally.^[5] PLMs seem to be common features within many people, and identifying whether or not these movements are clinically relevant for a distinct diagnosis of PLMD remains a challenge for clinical and scientific fields.^[4][5] Moreover, diagnosis of PLMD cannot be used when narcolepsy, restless legs syndrome (RLS), REM sleep behaviour disorder (RBD) or untreated obstructive sleep apnea (OSA) is already diagnosed, since abnormal movements during sleep are frequent in these disorders.^[3][4]