ABSTRACT
Periodic leg movements (PLMs) are repetitive, stereotyped flexor-withdrawal-like movements of the legs which occur during sleep. They can involve the arms and are thus called periodic limb movements of sleep (PLMS). PLMs can also occur during wakefulness [periodic limb movements of wake (PLMW)], especially in patients with restless legs syndrome (RLS) (1,2). Formerly, PLMS were called nocturnal myoclonus (3) due to their occasional myoclonic jerk character. With the purpose of emphasizing their repetitive periodicity and the fact that most PLMs did not reach the speed of a myoclonic phenomenon, the term periodic movements in sleep was introduced (4) later. After some time, the term was modified to PLMs in sleep: these movements involve the lower limbs in almost every case and were originally described as affecting exclusively the legs. However, the term periodic limb movements in sleep is better recommended, because in severe cases, the upper limbs and even the trunk can also be involved, that is, periodic arm movements (5).
