Periodic limb movements in sleep and periodic limb movement disorder

Previously referred to as “nocturnal myoclonus”, periodic limb movements in sleep (PLMS) is regarded as a distinct nosologic entity, although it overlaps a great deal with restless legs syndrome and other sleep disorders. While there is a lack of complete consensus on this matter, PLMS are regarded as pathological if more than five events occur per hour of sleep, and as a disorder (PLMD) if there is comorbid insomnia or daytime sleepiness in the absence of other symptoms. PLMS are common in healthy elderly individuals and have been reported to increase with age. The pathogenesis of PLMS is not clear. Lesion, imaging and laboratory studies indicate neuronal hyperexcitability with involvement of brain stem and spinal cord structures, in particular the central pattern generator for gait, and decreased dopaminergic transmission. Dopaminergic drugs, dopamine agonists, opiates, benzodiazepines and anticonvulsants are all used, with dopaminergic drugs or dopamine agonist regarded as first-line treatment.