Sleep myoclonus, restless leg disorder and periodic leg movement during sleep are sleep-related disorders that cause involuntary muscle twitches, jerks and spasms, according to the American Sleep Association. Sleep myoclonus rarely disturbs the affected individual or his sleep partner to the point of waking.
Sleep myoclonus may indicate the presence or development of the more serious restless leg disorder and periodic leg movement during sleep, explains the American Sleep Association. In addition, myoclonus is a leading sign of nervous system disorders such as Alzheimer’s, multiple sclerosis, epilepsy and Parkinson's disease.
Periodic leg movement during sleep causes movements every 20 to 40 seconds and can last for hours, states Healthline. The person is unaware of the movements and cannot control them.