Etiologies of Sleep-Related Movement Disorders (SRMD)

Sleep-related movement disorders (SRMD) encompass a group of relatively simple, stereotyped movements or monophasic movement disorders, such as periodic limb movement disorder (PLMD), sleep-related leg cramps, sleep-related bruxism, and sleep-related rhythmic movement disorder, that disturb sleep (American Academy of Sleep Medicine (2005) The International Classification of Sleep Disorders: Diagnostic and Coding Manual , 2nd edn. Westchester, IL: American Academy of Sleep Medicine). In addition, restless legs syndrome (RLS) has been included in this diagnostic category because of its close association with periodic leg movements during sleep. Common to all SRMD is a complaint of disturbed sleep, daytime sleepiness, or fatigue, which is a prerequisite for the diagnosis as opposed to a mere accidental finding during a nocturnal polysomnography. At the time of writing, the etiology of SRMD is unclear for all disorders. However, candidate systems have been identified for RLS (dopamine, iron, genetics) and PLMD (spinal processes).