Restless legs and periodic leg movements in sleep syndromes

Restless legs syndrome (RLS) is a common sensorimotor disorder with an estimated prevalence of between 1% and 5%. The symptomatology is characterized by unpleasant sensations experienced predominantly in the legs and rerely in the arms. The symptoms occur only at rest and become more pronounced in the evening or at night. In addition, the patients suffer from a strong urge to move the limbs, typically manifest as walking around, which leads to complete but only temporary relief of the symptoms. Most of the patients with RLS have periodic leg movements (PLMS) during sleep and relaxed wakefulness that are characterized by repetitive flexions of the extremities. PLMS can occur as an isolated phenomenon, but often they occur together with other sleep disorders including RLS, narcolepsy, sleep apnoea syndrome or REM sleep behaviour disorder. In all these disorders, PLMS contribute considerably to disturbed sleep, as the movements may lead to brief arousals or repeated full awakenings. The aetiology of RLS and PLMS is unknown. It is hypothesized that periodic leg movements result from a suprasegmental disinhibition of descending inhibitory pathways. Based on the efficacy of the drugs listed below, the dopaminergic, adrenergic and opiate systems are thought to play a major role in the pathogenesis of RLS/PLMS. Since the cause is unclear, therapy of RLS and PLMS remains symptomatic except for some secondary forms. Studies on the pharmacological treatment of RLS have shown the efficacy of levodopa, dopamine agonists, benzodiazepines, opioids, clonidine and carbamazepine. With regard to the drug treatment of PLMS in other sleep disorders including their isolated occurrence, indications and efficacy have been poorly defined until now.