Abstract
The state of normal sleep is characterized by diminished responsiveness to external stimuli and a familiar feeling of delight and refreshment. This feeling is accompanied by muscle relaxation and slowing of brain activity. Nevertheless, body movements are a feature of normal sleep and when those impair sleep quality and consequent daytime function they are defined as abnormal. The introduction of polysomnography during which muscle activity is monitored by electromyography and videotaping enabled sleep researches to precisely assess the characteristics of normal and abnormal movements, to determine their appearance is at specific sleep stages and to define their severity in regard to sleep quality and their impact on daytime function. Indeed, abnormal movements during sleep became an essential part of the symptomatology of a number of neurodegenerative disorders. Normal and abnormal movement disorder related to sleep onset, particular sleep stages and during awakening from sleep will be described in some detail. Common and rare forms of sleep related movement disorders in children and adults will be reviewed.