Original ArticleEarly manifestations of restless legs syndrome in childhood and adolescence☆
Introduction
Restless legs syndrome (RLS) is a neurological, sensorimotor disorder affecting sleep, which was first described over 300 years ago by Thomas Willis and further delineated by Karl Ekbom in the 1940s and 1950s [1], [2]. Although several large population-based studies have shown RLS to occur in 5–10% of adults in the United States and Western Europe [3], [4], [5], [6], [7], [8], [9], it has remained an underdiagnosed disorder [10], [11]. Age of onset has been reported retrospectively in three adult RLS studies, with onset prior to age 20 found in 27–38% and before age 10 in 8–13% [12], [13], [14]. Although Ekbom mentioned childhood RLS, it was not until the mid-1990s that detailed case reports of children and adolescents with RLS were published [15], [16], followed by several other pediatric studies [17], [18], [19], [20], [21], [22], [23], [24], [25], [26]. The first population-based epidemiological data on RLS in children and adolescents indicates a remarkable 2% prevalence in 8–17-year olds [27]. While emerging literature has begun to describe the clinical aspects of childhood RLS, much remains unknown.
In adults, RLS is a clinical diagnosis based on the patient’s history [28], [29]. There are four essential criteria for diagnosis: (1) an urge to move the legs, usually accompanied by uncomfortable leg sensations, (2) symptoms are worse when sitting or lying down, (3) symptoms are at least partially relieved by movement, and (4) symptoms are worse in the evening or at night than during the day. Other associated features commonly found in adults with RLS include sleep disturbance, periodic limb movements in sleep (PLMS), and a positive family history of RLS. While RLS can be mild in some cases, decreased quality of life ratings, cognitive deficits, attentional problems, and mood disorders are common in moderate to severe adult RLS [3], [30], [31], [32], [33], [34]. Problematic sleep is typical in individuals seeking treatment for RLS, with this feature present in more than 90% of patients in two large clinical series [13], [35]. Similarly, a recent population-based study reported sleep disturbance in 76% of adults with moderate to severe RLS [3]. “Secondary RLS” may occur in pregnancy, uremia, and spinal cord and peripheral nerve injuries, and due to some medications. Approximately 80–90% of adults with RLS have PLMS, which are brief extremity jerks that may be accompanied by transient arousals from sleep, cardiac acceleration, spikes in blood pressure, and sleep disruption [13], [36]. Periodic limb movement disorder (PLMD) is diagnosed when the following conditions are present: (1) PLMS exceeding norms for age, (2) clinical sleep disturbance, and (3) the absence of another primary sleep disorder or reason for the PLMS, including RLS [37]. Thus, an individual can have RLS with PLMS or have PLMD, but not both disorders.
In 2003, consensus criteria for the diagnosis of RLS in children and adolescents were published as the result of a meeting at the National Institutes of Health (NIH) in Bethesda, MD, USA (Table 1) [28]. Two major concepts were incorporated—more difficultly to achieve criteria for a definitive diagnosis in children 2–12 years old than in adults and separate research categories for less definitive cases. The first was agreed upon to avoid overdiagnosis in children and the second to provide a framework to investigate a potentially broader spectrum of RLS in childhood, thereby encouraging the inevitable evolution of these diagnostic criteria. Thus, definite, probable, and possible RLS categories were devised. In addition, anecdotal reports of PLMD developing into RLS over time in children were acknowledged, and refined PLMD criteria were developed. The NIH committee decided to use the adult criteria for adolescents, although the categories of probable and possible RLS were left open as an option for this age range of 13–18 years. PLMD criteria can be applied at any age, although frequency criteria are higher in adults than in children. These new pediatric RLS criteria and revised PLMD criteria were subsequently included in the International Classification of Sleep Disorders diagnostic manual, 2nd edition (ICSD-2) [37].
The purpose of this current study was to characterize the clinical aspects of an interesting group of children with RLS—those who presented initially with clinical sleep disturbance and did not meet definite RLS criteria but later in the course of follow-up did develop the essential symptoms for a definite RLS diagnosis. This is an important subset of children and adolescents with RLS because some of the early manifestations of RLS in childhood may help identify those who require clinical follow-up, may aid in proper diagnosis over time, and may provide insight into pediatric diagnostic criteria for RLS, especially for young children.
Section snippets
Methods
This is a retrospective chart review of cases of pediatric RLS in individuals who were initially evaluated before the age of 18 years at Carle Clinic Association, Urbana, IL, and were seen by a single physician (DLP). The practice setting is a large multispecialty clinic in a university community of approximately 110,000 with a referral base of about 300,000 from surrounding rural and small urban areas. At the time, this practice was about 40% child neurology and 60% sleep disorders. The study
Clinical characteristics and age of symptom onset
Eighteen children and adolescents were identified by chart review, who did not meet diagnostic criteria for definite RLS at initial presentation but did meet full RLS diagnostic criteria during follow-up care, out of 50 pediatric RLS cases in active follow-up. This represented 36% of our pediatric definite RLS cases at the time. There were 10 females and 8 males. Seventeen were Caucasian and one African-American/Caucasian.
Mean age at initial sleep evaluation was 10.3 years (range 0.2–17.1
Discussion
The most important finding of this case series is that in some children and adolescents clinical sleep disturbance can precede the full diagnostic manifestations of RLS by months or years. Such a clinical presentation occurred in 18 of 50 (36%) of our pediatric RLS cases at the time of this review with the interval between initial sleep consultation and development of definite RLS an average of 4.4 years. Remarkable was the recall of the onset of chronic clinical sleep disturbance an average of
Conclusions
In children and adolescents, clinical sleep disturbance and PLMD can precede the development of symptoms essential for a definitive diagnosis of pediatric RLS, suggesting a progression of symptoms over time.
Acknowledgments
Dr. Picchietti has received grant support from NIH R01 NS4 0829-02 and from the Carle Foundation.
This material was presented in abstract form at the 19th annual Association of Professional Sleep Societies Meeting in Denver, CO, June 2005.
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Dr. Picchietti receives grant support from NIH R01 NS4 0829-02 and from the Carle Foundation, and has served as a consultant to Boehringer Ingelheim and GlaxoSmithKline. This was not an industry-supported study.