Movement disorders are classically thought to resolve during sleep. Sleep-related movement disorders, however, are a subset that are characterized by their presence in sleep. This article will discuss these sleep-related movement disorders based on the International Classification of Sleep Disorders-3rd Edition (ICSD-3). These include restless legs syndrome, periodic limb movement disorder, sleep-related leg cramps, sleep-related bruxism, sleep-related rhythmic movement disorder, benign sleep myoclonus of infancy, propriospinal myoclonus at sleep onset, sleep-related movement disorders due to medical disorders, and sleep-related movement disorders due to medication or other substance.
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• Any patient suspected of having restless legs syndrome should be evaluated with serum ferritin as correction of iron-deficiency anemia may improve symptoms.
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• When treating restless legs syndrome, consider a nondopaminergic medicine first, and if a dopaminergic agent is used, try the lowest effective dose or long-acting formulation.
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• Periodic limb movements of sleep could be associated with increased cardiovascular risk due to transient elevations in blood pressure and heart rate.
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• Myoclonic movements isolated in sleep in an otherwise developmentally normal infant typically do not need treatment.
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• Sleep bruxism does not correlate with the presence or absence of pain symptoms.
Historical note and terminology
Movement disorders of sleep have been described for centuries. Perhaps the oldest sleep-related movement disorder described is sleep bruxism, which has been recognized since the time of the Old Testament. The term “bruxism” originated from the Greek brygmos, which means gnashing of teeth, and the first scientific description of bruxism was reported in the early 1900s (12). Similarly, restless legs syndrome was first described by Sir Thomas Willis in 1685; centuries later, Karl-Axel-Ekbom first used the term “restless legs syndrome” in 1944. Because of the pioneering work of these two individuals, restless legs syndrome now shares the name Willis Ekbom Disease (48).
In modern times, many sleep-related movement disorders are studied and treated within the specialties of both sleep medicine and movement disorder neurology. The American Academy of Sleep Medicine published the third edition of the International Classification of Sleep Disorders (ICSD-3) in 2014, and it is now widely used in clinical practice to characterize sleep disorders (04). The ICSD-3 recognizes seven broad categories of sleep disorders, including the following:
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• Sleep-related breathing disorders
• Central disorders of hypersomnolence
• Circadian rhythm sleep-wake disorders
• Sleep-related movement disorders
• Other sleep disorders
This article will highlight the nine sleep-related movement disorders listed in the ICSD-3 category of sleep related movement disorders. These include restless legs syndrome, periodic limb movement disorder, sleep-related leg cramps, sleep-related bruxism, sleep-related rhythmic movement disorder, benign sleep myoclonus of infancy, propriospinal myoclonus at sleep onset, sleep-related movement disorders due to medical disorders, and sleep-related movement disorders due to medication or other substance. Of note, REM behavior disorder will not be addressed in this article as it is defined not as a movement disorder of sleep but rather a type of parasomnia that is associated with various movement disorders.