Sensory symptoms in restless legs syndrome: the enigma of pain

Restless legs syndrome (RLS) is a common sensorimotor condition characterized by an urge to move the legs, worsening of symptoms at rest and during the evening/night, and improvement of symptoms with movement. Our review explores the role and impact of sensory symptoms in RLS. The phenomenology of RLS is discussed, highlighting the difficulty patients have in describing their sensations and in differentiating between sensory and motor symptoms. Sensory symptoms have a significant impact on quality of life but remain much less well understood than motor symptoms and sleep disturbances in RLS. Although RLS symptoms usually are not described as painful, sensory manifestations in RLS do share some similarities with chronic pain sensations, and RLS frequently occurs in chronic pain and neuropathic conditions. Peripheral neuropathies may account for some of the sensory disturbances in secondary RLS, while alterations in central somatosensory processing may be a more viable explanation for the sensory disturbances in primary RLS. The effectiveness of analgesics in treating RLS supports the concept of abnormal sensory modulation in RLS and suggests an overlap between pain modulatory pathways and sensory disturbances. Future studies are needed to better understand the experiential and biologic aspects of altered sensory experiences in RLS.