Periodic limb movement disorder, formally called sleep myoclonus or nocturnal myoclonus, is a type of sleep disorder in which arms and legs involuntarily twitch, cramp, or jerk during a sleep cycle. Periodic limb movement disorder generally affects the legs and feet more than arms. The most common movements include flexing of the toes, legs, and ankles. These movements may occur repetitively every minute or so during sleep and are more rhythmic and severe compared to the twitching that occurs normally when a person falls asleep. The condition does not show any symptoms while a person is awake; therefore, people who have the disorder are often unaware of the condition.
Restless leg syndrome, a nerve condition that causes uncomfortable sensations during lack of movement of the limbs, is sometimes misinterpreted as periodic limb movement disorder. However, periodic limb movement disorder is the only sleep condition that only becomes apparent during sleep only and generally has no indicators while a person is awake. Some identifiable symptoms of the disorder that a person may be able to recognize are if he or she wakes up often without warning, never falls into a deep sleep, or suffers from unexplained fatigue. Generally the disorder is brought to a doctor’s attention by a bed partner and is diagnosed using a sleep test called an overnight polysomnogram that records brain waves, chemical signals, and movements in the body while a patient is asleep.
There is no proven cause of periodic limb movement disorder; however, there are certain issues that may contribute to the disorder. Age may be a factor since people over the age of 60 are typically more likely to have the condition. Those with neurological disorders, such as Parkinson’s disease or narcolepsy, may also be more likely to suffer from periodic limb movement disorder. Nutritional deficiencies in iron or folic acid and some medications, such as antihistamines, antipsychotics, and antidepressants, can worsen the disorder. Patients with the disorder are also advised to avoid products that have caffeine, such as coffee, tea, or chocolate, since the chemical stimulants in the caffeine may increase the frequency and severity of the condition.
Although there is no cure for periodic limb movement disorder, it is typically treated with the same anticonvulsant medications and insomnia medications used to treat the tremors associated with Parkinson’s disease. In more severe cases, narcotics may be prescribed. These medications can reduce symptoms of the disorder to ensure the sleep movements do not continue to remain disruptive.