Periodic limb movements

Federica Provini MD (Dr. Provini of the University of Bologna and IRCCS Institute of Neurological Sciences of Bologna received speakers fees from Sanofi and Bial.)
Giacomo Chiaro MD (Dr. Chiaro of the University of Bologna and the Neurocenter of Southern Switzerland has no relevant financial relationships to disclose.)
Antonio Culebras MD, editor. (Dr. Culebras of SUNY Upstate Medical University has no relevant financial relationships to disclose.)
Originally released October 15, 1993; last updated January 30, 2017; expires January 30, 2020

This article includes discussion of periodic limb movements, nocturnal myoclonus, periodic leg movements, periodic limb movement disorder, periodic limb movements in sleep, periodic movements in sleep, PLMD, and PLMS. The foregoing terms may include synonyms, similar disorders, variations in usage, and abbreviations.

Overview

Periodic limb movements in sleep consist of flexion movements at the ankles, knees and hips, and sometimes the arms, recurring every 5 to 90 seconds, especially during light NREM sleep stages. Though representing an almost obligate accompaniment of restless legs syndrome and frequently associated with various neurologic and physical diseases, they are, however, also widely prevalent among the general population. In this article, the authors examine the clinical significance of periodic limb movements in sleep and advances in understanding the pathophysiology of this disorder. They review the treatment options now available, emphasizing that among the different therapeutic strategies, dopaminergic agents in particular have been shown effective in controlled trials. Finally, they discuss the possible role of periodic limb movements as a cardiovascular risk.

Key points

 

• Periodic limb movements are repetitive flexion movements of the toes, ankles, knees, and hips, sometimes the upper limbs too, lasting from 0.5 to 10 seconds that recur primarily in stage N1 and stage N2 of sleep with a periodicity of about every 5 to 90 seconds.

 

• Periodic limb movements may be associated with no EEG changes or with EEG evidence of arousal, and are preceded and associated with autonomic activation.

 

• Periodic limb movements in sleep tend to occur more frequently in the elderly population, and have been reported associated with several other medical conditions, but are especially frequent in restless legs syndrome.

 

• Periodic limb movement disorder is diagnosed when movements occur at a rate of more than 5 per hour in children or 15 per hour in adults, causing clinically significant sleep disturbance or impairment in mental, physical, social, occupational, educational, behavioral, or other important areas of functioning.

 

• Periodic limb movements in sleep respond to dopaminergic treatment.

Historical note and terminology

In 1953 Symonds coined the term "nocturnal myoclonus" to describe 5 diverse patients who had relaxed wakefulness and jerking of the extremities during sleep, which he thought could represent epileptic seizure (Symonds 1953). In the mid-1960s Lugaresi published a series of polysomnographic studies describing the EMG and EEG correlates of nocturnal myoclonus in patients with restless legs syndrome (Lugaresi et al 1965). Lugaresi and his colleagues also noted that nocturnal myoclonus can occur as an isolated phenomenon (Lugaresi et al 1966). In the late 1970s and early 1980s, Coleman, among others, pointed out that nocturnal myoclonus can occur in a wide variety of clinical conditions other than restless legs syndrome (Coleman et al 1980). Because nocturnal "myoclonus" tends to occur at 20- to 40-second intervals in sleep and is rarely myoclonic (less than 250 msec) during sleep, Coleman suggested the alternate term "periodic movements in sleep" (Coleman et al 1980). Subsequent terms include "periodic leg movements," which emphasizes the observation that the legs are primarily involved and "periodic limb movements in sleep," which emphasizes the observation that the arms may be involved as well. The American Academy of Sleep Medicine (AASM) uses the term "periodic limb movement disorder" when: A) polysomnography demonstrates periodic limb movements in sleep, as defined in the American Academy of Sleep Medicine Manual for the Scoring of Sleep and Associated Events (Berry et al 2014); B) the frequency is greater than 5 an hour in children or greater than 15 an hour in adults; C) the periodic limb movements in sleep cause clinically significant sleep disturbance or impairment in mental, physical, social, occupational, educational, behavioral, or other important areas of functioning; D) the periodic limb movements in sleep and the symptoms are not better explained by another current sleep disorder, medical or neurologic disorder, or mental disorder (eg, periodic limb movements in sleep occurring with apneas or hypopneas should not be scored) (American Academy of Sleep Medicine 2014). However, the AASM suggests that the periodic limb movements in sleep index, which quantifies the number of periodic limb movements per hour of sleep, must be interpreted in the context of a patient's sleep related complaint, emphasizing the importance of clinical context over an absolute cutoff value.

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