Restless legs syndrome (RLS) and periodic leg movements (PLM)

History In many ways, restless legs syndrome (RLS) is a bit of an oddity in this book on parasomnias. Its inclusion here reflects the somewhat tortured history of our understanding of this major sleep–wake disorder. RLS occurs as a sensorimotor neurological disorder primarily affecting what the great neurologist Critchely referred to as the pre-dormitum, i.e. that state before sleep enabling the entry to sleep. Thus RLS presents mostly as a sensory disorder disturbing the resting wake state, although it also appears to cause awakenings during sleep. Although a sensory disorder, it has a non-specific motor sign of periodic leg movements (PLM). These leg movements occur both as periodic events while resting awake (PLMW) and during sleep (PLMS). PLMS occurring during sleep meet the classic definition of a parasomnia. Table 22.1 presents the sometimes confusing terminology used in this chapter.The Oxford Don most famous for his description of the blood vessels at the base of the brain, the circle of Willis, in 1672 also provided the first medical description of RLS. His fine description of an RLS patient still aptly describes the night-time distress with moderately severe RLS (see Table 22.2).RLS after Willis remains largely ignored for the next 200 years. It is eventually described again in the nineteenth century in various forms often attributed to psychiatric problems, particularly anxiety. The Swedish Neurologist Karl Ekbom provided the first careful description of the disorder.