Restless Legs Syndrome and Periodic Limb Movement Disorder in Childhood and Adolescence

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Chapter 22 Restless Legs Syndrome and Periodic Limb Movement Disorder in Childhood and Adolescence

Until recently, restless legs syndrome (RLS) was generally believed to be a disorder of adults. However, multiple reports now document the occurrence of RLS, as well as the related problem of periodic limb movement disorder (PLMD), during childhood and adolescence.19 A recent population-based epidemiological study found an RLS prevalence of 2% in children ages 8 to 17 years.10 PLMD has been reported in 8.4% of children in a clinic-referred sample.11 Symptoms can range from mild to severe and in many cases can have a significant impact on a child’s quality of life.10 Thus, RLS and PLMD represent relatively common, medically significant pediatric disorders that are often not diagnosed. Advances in the understanding and treatment of these disorders permit an accurate diagnosis and effective treatment.

Periodic Limb Movement Disorder

Periodic limb movements in sleep (PLMS) are characterized by brief jerks during sleep (lasting 0.5 to 5.0 seconds), which typically occur at 20- to 40-second intervals.13,14 PLMS are more common in the toes, feet, and legs, than in the arms. The affected individual is usually not aware of the movements or of the associated transient arousals that disrupt sleep continuity. Between 80% and 90% of adults with RLS have PLMS.15 In healthy children and even young adults, PLMS rarely exceed five per hour.1618 Thus, the presence of PLMS of more than five per hour in children or adolescents supports a diagnosis of RLS (see later).19 PLMS, however, are not specific to RLS but also can be seen in some other sleep disorders and can be induced or aggravated by certain medications (particularly antidepressant medications).14,20 PLMD is diagnosed when there are (1) PLMS exceeding norms for age (>5 per hour for children), (2) clinical sleep disturbance, and (3) the absence of another primary sleep disorder or reason for the PLMS.14 In some children, a diagnosis of PLMD will evolve over time to a diagnosis of “RLS with PLMS” as the typical RLS feelings develop.

Diagnostic Criteria

Special criteria for the diagnosis of RLS were established for children at a National Institutes of Health (NIH) consensus conference on RLS.19 These criteria for childhood RLS should be used up to and including the age of 12 years, after which the adult criteria should be used. Several issues led to the development of separate criteria, which include (1) young children may have difficulty in describing the RLS feelings, (2) clinical experience indicates that children may report the RLS discomfort more during the day than at night or may not be able to determine when it is worse, and (3) a family history of RLS in a first-degree relative is likely relevant if a child meets some, but not all, of the adult criteria for RLS. However, the criteria for definite RLS were constructed as more difficult to fulfill than the criteria for adults because of a desire that false-positive diagnoses be avoided. Children can be diagnosed with definite RLS in either of two ways, as described in the table below (Table 22-1). Criteria for probable RLS and possible RLS were developed for research purposes (Tables 22-2 and 22-3).

TABLE 22-1 Criteria for the Diagnosis of Definite RLS in Children

Child meets all four of the following adult criteria:
• An urge to move the legs
• The urge to move begins or worsens when sitting or lying down
• The urge to move is partially or totally relieved by movement
• The urge to move is worse in the evening or night than during the day or only occurs in the evening or night
And
The child uses his or her own words to describe leg discomfort.
Examples of age-appropriate descriptors: oowies, tickle, tingle, static, bugs, spiders, ants, boo-boos, want to run, and a lot of energy in my legs.
OR
Child meets all four of the above adult criteria
And
Two or three of the following supportive criteria:
• Sleep disturbance for age
• Biological parent or sibling has definite RLS
• The child has a sleep study documenting a periodic limb movement index of 5 or more per hour of sleep

TABLE 22-2 Criteria for the Diagnosis of Probable RLS in Children

The child meets all essential adult criteria for RLS, except criterion #4 (the urge to move or sensations are worse in the evening or at night than during the day)
And
The child has a biological parent or sibling with definite RLS
OR
The child is observed to have behavior manifestations of lower-extremity discomfort when sitting or lying down, with motor movement of the affected limbs. The discomfort has characteristics of adult criteria 2, 3, & 4: worse during rest and inactivity, relieved by movement, and worse during the evening and night.
And
The child has a biological parent or sibling with definite RLS

TABLE 22-3 Criteria for the Diagnosis for Possible RLS in Children

The child has periodic limb movement disorder
And
The child has a biological parent or sibling with definite RLS, but the child does not meet definite or probable childhood RLS definitions.

Source: The NIH RLS workshop. RLS: Diagnosis and Diagnostic and Epidemiological Tools (2003).19

Prevalence, Impact, and Relationship to “Growing Pains”

A large epidemiological study applied the NIH workshop diagnostic criteria to a population-based questionnaire survey of families with children in the United States and the United Kingdom.10 Definite RLS criteria were met by 1.9% and 2% of all children ages 8 to 11 and 12 to 17 years, respectively. RLS occurring = 2/week and causing moderate to severe distress when present had been identified by a panel of experts as indicating clinically significant RLS for adults, likely to benefit from treatment.21,22 In the pediatric study, 0.5% of children ages 8 to 11 years and 1.0% of those ages 12 to 17 years reported symptoms meeting these criteria for clinically significant RLS. There were no significant gender differences. A family history of RLS was common, with 70% of all children diagnosed with definite RLS having a biological parent who reported symptoms consistent with a diagnosis of RLS, including 16% for whom both parents had RLS symptoms. The children with definite RLS symptoms, compared with the non-RLS children, more commonly reported sleep disturbance (69% versus 40%, p <.001). In addition, children with clinically significant RLS reported a high rate of adverse consequences from the RLS symptoms, such as negative mood (59% to 68%), decreased energy (51% to 59%), and inability to concentrate on school work (41% to 45%) (Fig. 21-1).

image

FIGURE 22-1. Perceived consequences of restless legs syndrome (RLS) for children and adolescents with moderate-severe RLS symptoms.

Reprinted with permission from Picchietti D, Allen RP, Walters AS, et al. Restless legs syndrome: prevalence and impact in children and adolescents—The Peds REST study. Pediatrics 2007;120:253-266.

Six other studies have reported pediatric-onset RLS prevalence data and one has reported pediatric PLMD prevalence data. A study of 1084 unselected children from 12 pediatric practices found RLS to affect 1.3%.23

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