Restless legs syndrome (RLS) is a sensorimotor disorder, characterized by an irresistible urge to move the legs and usually accompanied or caused by uncomfortable and unpleasant sensations. It begins or worsens during periods of rest or inactivity, is partially or totally relieved by movement and is exacerbated or occurs mainly in the evening or night. People suffering from RLS are estimated to represent 2-3% of the general Japanese population, which is relatively lower than the estimated prevalence in western countries. Supportive diagnostic critevia include family history, the presence of periodic-leg movements (PLM) when awake or asleep, and a positive response to dopaminergic treatment. RLS phenotypes include an early onset form that is usually idiopathic with frequent familial history and a late onset form that is usually secondary to other somatic conditions that are causative factors in RLS occurrence. In all patients presenting with complaints of insomnia or discomfort in the lower limbs, diagnosis of RLS should be considered. RLS should be differentiated from akathisia, which is an urge to move the whole body in the absence of uncomfortable sensations. Polysomnographic studies and the suggested immobilization test (SIT) can detect PLM in patients that are asleep or awake. RLS may cause severe sleep disturbances, poor quality of life, depressive and anxious symptoms, and may be a risk factor for cardiovascular disease. Secondary RLS may occur due to iron deficiency, end-stage renal disease, pregnancy, peripheral neuropathy and drug use including antipsychotics and antidepressants. Small fiber neuropathy can trigger RLS or mimic its symptoms. RLS is associated with many neurological disorders, including Parkinson disease and multiple system atrophy; althoughit does not predispose to these diseases. A symptom rating scale for RLS authorized by the International RLS Study Group (IRLS) would facilitate accurate diagnosis of this condition.
