The term restless legs syndrome (RLS) was used initially in the mid-1940s by Swedish neurologist Karl A. Ekbom to describe a disorder characterised by sensory symptoms and motor disturbances of the limbs, mainly during rest. However, early descriptions date back to the 17th century. It is recognised now as a neurologic movement disorder of the limbs, often associated with a sleep complaint. Patients with RLS have a characteristic difficulty in trying to depict their symptoms; they may report sensations such as an almost irresistible urge to move the legs, which are not painful but are distinctly bothersome; this can lead to significant physical and emotional disability. The sensations usually are worse during inactivity and often interfere with sleep, leading to walking discomfort, chronic sleep deprivation, and stress. Once correctly diagnosed, RLS can usually be treated effectively by relieving symptoms; in some secondary cases, it can even be cured.
Pathogenesis of RLS is unclear. Ekbom originally proposed that it was mainly the result of accumulation of metabolites in the legs because of venous congestion. Peripheral nerve abnormalities also have been proposed, but no associated structural changes in nerve endings have been identified.
RLS also has been linked to dopaminergic or opiate abnormalities. Centrally acting dopamine receptor antagonists reactivate symptoms when given to patients with the syndrome. Results of single-photon emission computed tomography (SPECT) have suggested deficiency of dopamine D2 receptors. Sympathetic hyperactivity also has been implicated on the basis of observations that sympathetic nerve blockade relieves periodic limb movements of sleep and that alpha-adrenergic blockers improve symptoms of RLS. Studies also have suggested possible under activity of the serotonin and gamma-aminobutyric acid (GABA) neurotransmitter systems.
The severity of symptoms in patients with RLS ranges from mild to intolerable. Although patients experience the sensations in their legs, they also may occur in the arms or elsewhere. RLS symptoms are generally worse in the evening and night and less severe in the morning. While RLS may present early in adult life with mild symptoms, usually by age 50 it progresses to daily severe disruption of sleep leading to decreased daytime alertness. RLS is associated with reduced quality of life in cross-sectional analysis.
A childhood-onset restless legs syndrome has also been described. A study published in Dec 2004 by Kotagal and Silber concluded that iron deficiency and a strong family history were characteristic of this childhood-onset presentation.