Chapter 29: Parasomnias and Sleep-Related Movement Disorders

RESTLESS LEGS SYNDROME AND PERIODIC LIMB MOVEMENT DISORDER

Diagnostic Essentials

Restless legs syndrome (RLS) is a common sensorimotor neurologic disorder with symptoms in both wakefulness and sleep. It affects 5% to 10% of adults, with up to 38% of adults reporting the onset of symptoms in childhood and 8% to 13% reporting symptoms before age 10.¹ RLS is a clinical diagnosis with 4 essential symptom criteria: (1) an urge to move the legs, usually in association with or due to uncomfortable sensations in the legs; (2) symptoms that begin or worsen during rest or inactivity (ie, sitting or lying down); (3) partial or complete relief of symptoms with movement; and (4) symptoms that are only present or become worse at night (Table 29–1). RLS is a unique clinical entity, and therefore, the symptoms cannot be due to other conditions such as muscle cramps, neuropathies, or positional discomfort.^2,3

General Considerations

Eliciting the typical symptoms of RLS in children is especially challenging, limited often by the child’s ability to describe sensations that cause discomfort but are frequently not painful. As such, special considerations should be made when assessing the quality of RLS symptoms described by children.³ Common descriptive terms used by children include creepy-crawlies, ants crawling, jittery, worms moving, shock-like feelings, burning, throbbing, tight feelings, fidgety, and itchy bones.⁴ Caregivers may report restlessness in bed with limb jerks or leg kicking, difficulty falling or staying asleep, and daytime consequences such as fatigue or behavioral symptoms.

Etiology and Pathogenesis

The pathophysiology of RLS has not been fully elucidated, although brain iron deficiency related to abnormalities of central nervous system iron transport and/or iron storage is thought to be a primary cause.^5,6 Secondary causes of RLS include disorders related to iron metabolism or iron deficiency including chronic renal disease, iron deficiency anemia, and pregnancy. Circadian dysregulation of dopaminergic neurons⁷ may explain the treatment response to dopaminergic agents as well as the exacerbation of symptoms seen with antidopaminergic medications (antiemetics, antipsychotics). Pediatric RLS shows a high degree of heritability, with up to 80% children with RLS having one parent with symptoms of RLS.⁸ Genome-wide association studies have identified several genetic polymorphisms, including at BTBD9, that increase the risk for RLS.⁹

Clinical Findings

RLS is a clinical diagnosis, and all 4 of the typical URGE symptoms (see Table 29–1) are necessary to establish the definite diagnosis in adults. Therefore, polysomnography ...