Periodic limb movement disorder involves repetitive movements of the arms, legs, or both during sleep. Restless legs syndrome involves an irresistible urge to move and usually abnormal sensations in the legs, arms, or both when people sit still or lie down.
These disorders are more common during middle and older age. Restless legs syndrome probably affects 1 to 2% of people. It is particularly common among people older than 50. Most people with restless legs syndrome also have periodic limb movement disorder, but the reverse is not true.
What causes these disorders is unknown. But one third or more of people with restless legs syndrome have family members with the syndrome. Risk factors include a sedentary lifestyle, smoking, and obesity. Periodic leg movement disorder is common among people with narcolepsy and rapid eye movement (REM) behavior disorder. Both disorders are more likely in people who have or do the following:
Both disorders interrupt sleep. As a result, people feel tired and sleepy during the day.
In periodic limb movement disorder, the legs or arms typically twitch and jerk every 20 to 40 seconds during sleep. People are unaware of these movements and the brief awakenings that follow. People do not have any abnormal sensations in their legs or arms.
Typically, people with restless legs syndrome have an irresistible urge to move their legs when they are sitting still or lying down. People also often feel vague but intense strange sensations in their legs, sometimes accompanied by pain. The sensations may be described as burning, creeping, or tugging or like insects crawling inside the legs. Walking or moving or stretching the legs can relieve the sensations. People may pace, constantly move their legs while they are sitting, and toss and turn in bed. Thus, people have difficulty relaxing and falling asleep. During sleep, the legs may move spontaneously and uncontrollably, often awakening the sleeper. Symptoms are more likely to occur when people are under stress. Episodes may occur occasionally, causing few problems, or several times a week, depriving people of sleep and making it difficult to concentrate and function.
Doctors can often diagnose restless legs syndrome based on symptoms reported by the person or the person's bed partner.
Polysomnography, including electromyography (EMG), is always done to diagnose periodic limb movement disorder. These tests are done overnight. In polysomnography, brain activity, heart rate, breathing, muscle activity, and eye movements are monitored while people sleep. People may be videotaped during an entire night's sleep to document limb movements.
If either disorder is diagnosed, blood and urine tests are done to check for disorders that can contribute, such as anemia, iron deficiency, and kidney and liver disorders.
Avoiding caffeine, which can make symptoms worse, is recommended. Taking vitamin and mineral supplements that contain iron may help.
There is no proven treatment for periodic limb movement disorder, although many of the treatments used for restless legs syndrome also help. There are a number of effective treatments for restless legs syndrome.
Last full review/revision January 2013 by Karl Doghramji, MD