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MedGenMed. 2006; 8(2): 79.
Published online Jun 20, 2006.
PMCID: PMC1785221

Restless Legs Syndrome in Children

Murali Maheswaran, DO, Staff Physician and Clete A. Kushida, MD, PhD, Associate Professor; Director

History and Introduction

Restless legs syndrome (RLS) is a neurologic disorder that was first described in the medical literature by T. Willis in 1672.[1,2] More than 250 years later, in 1945, Karl Ekbom applied the phrase “restless legs” to the syndrome.[3,4] Ekbom later wrote a paper on “growing pains” and “restless legs” and differentiated between them because growing pains were generally presumed to last only through childhood, whereas RLS had an early onset but was believed to persist into adulthood.[35] In 1960, Brenning noted that complaints of growing pains in children correlated with a higher risk of developing RLS-like symptoms as adults.[3,4] Primary RLS is believed to be an autosomal dominant disorder and, recently, scientists located a gene associated with RLS susceptibility on chromosome 12q for French-Canadian families, 14q for an Italian family, and 9p for 2 American families.[6,7]

RLS is a sensory and motor disorder characterized by an uncontrollable sensation in the legs accompanied by an irresistible urge to move the legs, which usually results in partial or complete resolution immediately, albeit transiently.[7] There are many subtle variations of this disorder. To complicate matters, the diagnosis is purely clinical and thus depends on accurate historians to convey their subjective complaints. This poses a problem, especially in children. Consequently, RLS in children is believed to be underdiagnosed. Because primary care physicians typically comprise the frontline for the diagnosis and treatment of this disorder, accurate assessment by this physician population is critical. Children with RLS can present with conduct problems including aggression, inattention, hyperactivity, and daytime somnolence because of an inability to sleep or difficulty maintaining sleep. These symptoms may result from an associated periodic limb movement disorder (PLMD) or other problems such as aches and pains.[8] The consequences of RLS can be serious and include unsatisfactory performance in school, poor social development, and abnormal social interactions resulting in incorrect diagnoses of various psychiatric illnesses, including attention deficit hyperactivity disorder (ADHD), among others.

Readers are encouraged to respond to George Lundberg, MD, Editor of MedGenMed, for the editor's eyes only or for possible publication via email: ten.epacsdem@grebdnulg

Diagnosis

Four of the essential criteria for RLS in adults are similar in children, but children require additional components depending on a diagnosis of definite or probable childhood RLS. The 4 essential diagnostic criteria for adults are:

  1. An urge to move the legs, usually accompanied or caused by uncomfortable and unpleasant sensations in the legs;
  2. The urge to move or unpleasant sensations beginning or worsening during periods of rest or inactivity such as lying or sitting;
  3. The urge to move or the unpleasant sensations are worse or only occur in the evening or night; and
  4. The urge to move or unpleasant sensations are partially or totally relieved by movement, such as walking or stretching, at least as long as the activity continues.[7,911]

For a diagnosis of definite childhood RLS, the child must meet all 4 essential adult criteria for RLS and describe the sensations in his or her own words. If the child is unable to describe the symptoms that are consistent with leg discomfort, then at least 2 of the following must be present: (1) sleep disturbance not typical for age; (2) a biological parent or sibling with definite RLS; and/or (3) a polysomnogram (PSG) documenting a periodic limb movement index of 5 or more movements per hour of sleep.[9,11]

For the diagnosis of probable childhood RLS, the child's family must have a history of definite RLS (biological parent or sibling only). In addition, the child either must meet all 4 diagnostic criteria for RLS or must be observed to have behavioral manifestations of lower-extremity discomfort when sitting or lying down, accompanied by motor movement of the affected limbs.[911] For the diagnosis of possible childhood RLS, the child who does not meet the definite or probable childhood RLS definition must have PLMD and a family history of definite RLS (biological parent or sibling only).

Epidemiology and Clinical Characteristics

The exact prevalence of RLS in children is unknown, although some data have been reported in restricted populations. For example, a study performed at the Mayo Sleep Disorders Center showed a prevalence of RLS in children aged 18 years or younger to be 5.9%. In this population, 32 of the 538 subjects fulfilled criteria for either definite or probable RLS.[10] Other studies have shown between 38% and 45% of adults with RLS experienced onset of symptoms before they were 20 years of age.[12,13]

Clinical Characteristics

Typically, RLS follows a circadian pattern, usually occurring in the evening or night but, rarely, at other times during the day. Children can be especially “restless” in cramped, restrictive situations such as when seated in a classroom, movie theater, airplane, or automobile. The children may be labeled “fidgety” and overactive. The RLS sensations (Table 1) are partially or completely resolved with motor movements or actions involving the lower extremities like walking or running, rubbing, stretching, or kicking the legs. Conscious effort to stop motor movements or actions can be achieved by a child usually only for a short period of time, similar to that of a child with motor tics. Emotional social interactions also can thwart or alleviate the restless symptoms. Hot or cold sensations may partially reduce symptoms in childhood RLS just as they relieve growing pains, muscle pains, and leg cramps. These overlapping clinical manifestations can make it difficult to differentiate between the other common diagnoses given to children (see Differential Diagnosis of RLS).

Table 1
Common Subjective Terms for Reporting Sensations of RLS in Children[4,11]

“Pain” is a term commonly used to describe the uncomfortable sensations in children with RLS. But the more pain the child complains of, the less likely it is RLS. RLS-related pain in children typically occurs from both knees down and especially involves the calves, although thigh pain may also appear. These pains can be symmetric or asymmetric. Partial or complete resolution by movement is a key feature when diagnosing RLS in children with pain complaints. Complaints of disrupted sleep may also be common; disrupted sleep in children with RLS often results from periodic limb movements in sleep (PLMS). Approximately 80% of adults with RLS have evidence of PLMS with PSG.12 The 2005 revised International Classification of Sleep Disorders states that 80% to 90% of patients with RLS will have PLMS on PSG.[7] Less clear is whether a similar relationship for RLS and PLMS exists for children with RLS. Of interest, both RLS and PLMS appear to be common in children with conduct disorders who present with aggressive behaviors and/or characteristics of ADHD.[8,14,15]

Disrupted sleep in children with obstructive sleep apnea (OSA) and differences in daytime presentations among children and adults have been observed.[16] Children with sleep-disordered breathing (SDB) may present with hyperactivity rather than excessive daytime somnolence, which is more common in adults. Other daytime symptoms in children with SDB are lack of concentration, irritability, mood changes, and restlessness, and these may be indiscernible from similar symptoms in children with RLS. Thus, children with RLS with or without PLMD causing disrupted sleep may exhibit many daytime symptoms that are similar to those observed in children with SDB.[16]

Differential Diagnosis of RLS

Growing Pains

Rajaram and colleagues define growing pains as “Ill-defined limb discomforts in children that do not meet criteria for other diagnoses, such as arthritis, other bone and joint pathology, peripheral neuropathy, and radiculopathy.”[4] Growing pains can be difficult to differentiate from RLS. A similar characteristic of both is the circadian pattern of the symptoms, which occur in the late afternoon to bedtime. Growing pains differ from RLS in that the unpleasant sensations are not partially or totally relieved by movements of the lower extremities. Typically, children may awaken in the middle of the night complaining of a “throbbing” pain in the legs. Onset usually occurs during early to late childhood, and the location of the pain is prominent in the front of the thighs, calves, or behind the knees. Symptoms may be alleviated with massage, ice packs, warm compresses, and acetaminophen or ibuprofen.

Motor Tics

Motor tics may involve 1 or more muscle groups. Common simple tics involving 1 muscle group are eye blinks, facial twitches or grimacing, head shaking, shoulder shrugging, and neck or leg jerking. Tics are involuntary but can be temporarily suppressed with voluntary effort, although most children experience an urge to act out that grows as the tics build up. Commonly after voluntary suppression, a cluster of tics occurs, resulting in great relief for the individual. Typically, the diagnosis occurs at about age 7, and it is more common in boys. Tics are believed to be an inherited neurologic disorder that usually resolves by adulthood, although sometimes it may persist.

Attention-Deficit/Hyperactivity Disorder (ADHD)

The exact relationship of ADHD, RLS, and PLMD is unknown, and there appears to be an overlap of symptoms and treatment. All 3 of these disorders can present with irritability, mood changes, hyperactivity, inattention, and motor restlessness. It has been demonstrated that RLS and PLMD frequently are seen in children diagnosed with ADHD. To further complicate the issue, RLS, PLMD, and ADHD all respond to dopaminergic agents, and dopaminergic deficits have been suspected as an etiology for both RLS and ADHD through brain imaging studies. ADHD may be overdiagnosed, and children suspected of this disorder should be evaluated for RLS, PLMD, and OSA by a sleep specialist or a pediatric neurologist.

Muscle Pain

This condition is more painful and cramp-like than RLS. It is usually associated with strenuous activity or exercise, typically is restricted to isolated muscle groups, and is not relieved by movement of the affected limb(s).

Leg Cramps

Unlike RLS, leg cramps are very painful, typically affect 1 leg, and are restricted to a specific muscle group(s). Symptoms are not relieved by leg movements and are alleviated by rest and alternate use of ice packs and warm compresses. Electrolyte disturbances and neuromuscular disorders may be an underlying etiology, especially in severe cases. Nocturnal leg cramps are also relatively common in children. Leung and colleagues[17] found that the incidence of nocturnal leg cramps increased at age 12 years and peaked at age 16 to 18 years; the overall incidence in the study group was 7.3% of healthy children.

Osgood-Schlatter's Disease

This disorder results in complaints of knee pain that worsens after strenuous activity or activities that require excessive kneeling or movement of the knee. Typical age of onset is between 10 and 14 years of age and is believed to be caused by an abnormal strain of the patellar tendon that causes pain at the site of attachment at the knee cap. There is no circadian pattern. Ice packs alternating with warm compresses and medications such as acetaminophen and ibuprofen may provide temporary relief. For persistent pain, a referral to an orthopaedist may be prudent.

Chondromalacia Patella

This condition is also known as patellofemoral pain, idiopathic anterior knee pain, or patellofemoral malalignment syndrome. It is a diagnosis of exclusion that typically results from malalignment or maltracking of the patella femoral joint, which causes damage to the underside of the patella. The worst pain occurs with the knee in full flexion. Unlike RLS, pain is at the knee joint and movement precipitates the pain. Nonsteroidal anti-inflammatory drugs, ice massage or heat, avoiding activities that cause pain such as leg squats or bike riding, and orthopaedist-prescribed reconditioning techniques such as straight leg raises or orthotics may be appropriate treatments.[18]

Arthralgias

Arthralgias comprise many medical disorders that involve joint pain. Unlike RLS, swelling and tenderness may be present at the affected joint(s) and the pain may be more severe. Systemic involvement of muscles and nerves may arise and, depending on the medical disorder, may mimic some of the complaints seen in RLS.

SDB and PLMD

SDB and PLMD can cause fragmented sleep and impaired sleep quality, which in turn result in daytime symptoms (eg, irritability, mood changes, lack of concentration, restlessness) similar to those seen in children with RLS. However, children with SDB or PLMD may present with symptoms such as hyperactivity, conduct disorders, and enuresis, which are different from those seen in adults. The most common cause of SDB in children is adenotonsillar hypertrophy.

Akathisia

This syndrome consists of a subjective feeling of inner restlessness followed by an urge to move. Unlike RLS, this condition is usually a drug-induced adverse effect of antipsychotics and may occur at any time during the day. The treatment of choice is withdrawal or reducing the dose of the offending agent. If this fails, lipophilic beta blockers such as propranolol have been shown to be effective. Other medications that are used occasionally include benzodiazepines, clonidine, amantadine, amitriptyline, and opioids.

Etiology

Central dopaminergic systems are involved to some extent in the pathogenesis of RLS, based on the fact that dopaminergic medications improve RLS symptoms. Primary RLS is believed to be inherited, and evidence indicates that it may be an autosomal dominant disorder. Some RLS-susceptibility loci have been found, and it is believed that other loci may be involved.[6]

The most common cause of secondary RLS in children appears to be iron deficiency. Iron is integral for the biosynthesis of dopamine; it is necessary for tyrosine hydroxylation, which is a rate-limiting step for dopamine production. The levels of serum ferritin in children that are considered normal vary according to age and sex.[10] Kotagal and Silber[10] found that serum ferritin levels in children with RLS were low in a large percentage of subjects who fulfilled the strict criteria of children with definite and/or probable RLS. They found that 33% of children with RLS had serum ferritin below the 5th percentile, 75% below the median (23 micrograms (mcg)/L in males and 17 mcg/L in females), and 83% below 50 mcg/L.[10] The 50 mcg/L level was selected because of its association with greater severity of RLS.[19] Kotagal and colleagues[10] found that almost 6% of children seen at their sleep center had either definite or probable RLS, and the most common risk factors were iron deficiency and a family history of RLS.

Research has not yet determined whether this iron deficiency is associated with diet or a genetic predisposition, but a combination of both may be the most likely explanation. Other causes of secondary RLS include peripheral neuropathy and uremia. Medications, such as antidepressants (eg, tricyclic antidepressants [TCAs], selective serotonin reuptake inhibitors [SSRIs]), sedating antihistamines, and dopamine receptor antagonists, may worsen or precipitate cases of RLS.[7]

Treatment

Treatment of RLS in children is controversial, and opinions differ among many sleep physicians primarily because there have been no randomized placebo-controlled trials for the treatment of RLS or PLMD in this population. In their practice parameters for RLS and PLMD, the Standards of Practice Committee of the American Academy of Sleep Medicine states that no specific recommendations can be made regarding treatment of children with RLS and PLMD.[20,21]

Certain medications have been tried in children with RLS, including levodopa/carbidopa, dopamine agonists (eg, ropinirole, pramipexole), benzodiazepines (eg, clonazepam), and alpha-adrenergics (eg, clonidine). Currently, the US Food and Drug Administration has approved no medications for RLS in children, although ropinirole has been approved for the treatment of moderate-to-severe primary RLS in adults. The long-term risks of treating children for RLS or PLMD with the existing medications are unknown. Clonidine and clonazepam have been studied in children with RLS, and both medications are fairly well tolerated. However, clonazepam should be used with caution in children suspected of sleep-disordered breathing because it can relax the upper airway muscles, thereby increasing the likelihood of upper airway collapse. Dopaminergic medications may be considered in children with severe cases of RLS, although the long-term effects are unknown. They are generally well tolerated in children; however, up to 20% of children taking carbidopa/levodopa may develop nausea. Several case studies demonstrate good efficacy and tolerance of carbidopa/levodopa and ropinirole in children with ADHD and RLS.[22,23]

The best initial form of treatment is to reduce factors or conditions that may worsen or precipitate RLS. Iron deficiency should be considered in a child with RLS. Measuring serum ferritin is recommended, but it should not be tested in ill children; it can be falsely elevated because ferritin is an acute-phase reactant. No guidelines have been formulated for treating iron deficiency in children with RLS. Thus, iron supplementation should be implemented with caution, and some pediatricians may recommend multivitamins containing iron rather than ferrous sulfate. It may take weeks or months of treatment with iron supplementation to detect improvements in RLS symptoms.

Good sleep hygiene practices can be helpful for children with RLS. These include enforcing a regular sleep-wake schedule; avoiding heavy meals, fluids, or exercise within a few hours of bedtime; and discouraging non-sleep-inducing activities such as watching television or playing games near bedtime.

Medications such as SSRIs and TCAs can precipitate RLS or PLMD in predisposed individuals, and switching to another class of antidepressants is recommended. Caffeine, sedating antihistamines, and dopamine antagonists such as compazine and metaclopramide may also worsen RLS.

Conclusions

The diagnosis and treatment of RLS in children is often challenging. The RLS diagnosis in children is often hampered because children may be unable to provide a good description of the symptoms. Furthermore, many conditions and disorders can mimic RLS. If it is not treated, RLS in children can result in serious behavioral consequences, including impaired daytime functioning, poor school performance, and poor social interactions stemming from conduct disorders.

Medications are available for the treatment of RLS in adults, but the effectiveness and adverse effects of these medications in children are unknown. Factors or conditions that may worsen or precipitate RLS in children have yet to be explored. Pediatricians should be aware that this condition can be accurately diagnosed by obtaining a thorough history, and that treatment, though limited at this point, can reduce the symptoms of this common disorder.

Contributor Information

Murali Maheswaran, St. Luke's Health System, Kansas City, Missouri.

Clete A. Kushida, Stanford University Medical Center; Stanford University Center for Human Sleep Research, Stanford, California.

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