Rhythmic movements in sleep disorders and in epileptic seizures during sleep

Rhythmic movements during sleep may occur in the context of physiological sleep-related motor activity or be part of sleep-related movement disorders such as bruxism, periodic limb movement disorder, restless legs syndrome, and sleep-related rhythmic movement disorder. They may also characterize some frontal or temporal nocturnal seizures of sleep-related hypermotor epilepsy, or be considered as part of NREM parasomnias, especially sleepwalking, sexsomnia or sleep-related eating disorder, or REM-related behaviors such as REM behavior disorder or complex movements associated with pediatric narcolepsy type I. In most cases rhythmic movements, especially when complex and long in duration, are related to different levels of arousal from sleep with recurrence of ancestral motor sequences promoted by central pattern generators in the brainstem, generally activated by the arousal process. A differential diagnosis between physiological events and pathological movement disorders, and between the latter and sleep-related epilepsy is critical to provide optimal treatment and an accurate prognosis. Specific treatment options for the aforementioned disorders are beyond the scope of this article.