Periodic limb movement disorder (PLMD) is a sleep disorder in which you involuntarily and unconsciously extend and flex muscles in your legs and arms when you are asleep. PLMD is sometimes known as Periodic Limb Movements of Sleep (PLMS) or nocturnal myoclonus. If you have periodic limb movement disorder, you may move your legs or arms hundreds of times during the night, twitching and kicking – possibly even kicking or hitting a bed partner.
Each muscle movement lasts for about half a second to about five seconds. Muscle movements take place every twenty to forty seconds.
Usually, these movements occur only during NREM sleep, most commonly during Sleep Stage 1 or Sleep stage 2. Normally, your arms and legs are paralyzed during REM sleep. Limb movements are more likely to take place at the beginning than at the end of the night.
People with periodic limb movement disorder are more likely to move their legs than their arms in their sleep. A common sequence of leg movements starts with a flexing of the big toe. Muscle movement may then travel upwards, so that the ankle, then the knee, and then finally the hip are bent. Muscle movement may occur only in one leg, or may switch back and forth between legs. If PLMD affects your arms, you may repeatedly flex your elbow.
Periodic limb movement disorder is associated with Restless Leg Syndrome (RLS). Restless leg syndrome is a condition in which the sufferer feels unpleasant sensations, such as tingling, itchy or burning sensations, in their arms or legs. These sensations are relieved when the affected limbs are moved.
About 80% of people with restless leg syndrome also suffer from periodic limb movement disorder.
Periodic limb movement disorder is more common in people over 65 than in younger people.
People with Parkinson’s Disease, narcolepsy and REM sleep behavior disorder are more likely to suffer from PLMD than people who do not suffer from any of these conditions.
Many women suffer from periodic limb movement disorder temporarily when they are pregnant.
Symptoms of Periodic Limb Movement Disorder
If you suffer from periodic limb movement disorder, you will not be aware of your limb movements during the night. However, you may wake up to find that your bed sheets have been moved around or kicked off the bed. If you share a bed with someone, your bed partner may complain about your movements.
Periodic limb movement disorder can cause you to awaken frequently during the night and to feel very sleepy during the day. Lack of sleep can make you feel irritable or cause you have trouble concentrating.
Because the limb movements that characterize periodic limb movement disorder take place during the sleep stages that precede REM sleep, you may frequently wake up before you reach REM sleep. This can cause you to suffer from a deficiency of REM sleep, which can in turn to cause you to become irritable, to be more sensitive to pain, and to have difficulty remembering things.
Sometimes children suffer from periodic limb movement disorder. They may be irritable or hyperactive during the day, and they may have difficulty in school.
Causes of Periodic Limb Movement Disorder
Scientists do not know exactly what causes PLMD.
Periodic limb movement disorder can be a symptom of iron deficiency or folic acid deficiency. It is also associated with diabetes, uremia, injury to the spinal cord and heart failure.
People with PLMD sometimes also suffer from obstructive sleep apnea.
Because people with PLMD tend to move their limbs more at the beginning than at the end of the night, some scientists think that PLMD may be a circadian rhythm disorder that is related to problems with the production of melatonin.
Caffeine, antihistamines, and some antidepressants and anti-psychotics can make PLMD worse.
Diagnosis of Periodic Limb Movement Disorder
If you feel very sleepy during the day, you wake up frequently, or your bed partner complains that you move around a lot when you sleep, your doctor may recommend that you have a polysomnogram, or sleep study, to determine if you have periodic limb movement disorder or any other parasomnia (sleep disorder), such as sleep apnea or narcolepsy.
During a polysomnogram, sensors are attached to your head and different parts of your body, and a device to measure the oxygen level in your blood is clipped to one of your fingers.
You then go to sleep.
As you sleep, your brain waves, breathing, heart rate, blood pressure, blood oxygen levels and muscle movements throughout the night are recorded.
Treatment of Periodic Limb Movement Disorder
If you suffer from periodic limb movement disorder, you should try to reduce your caffeine intake. If medication is making your PLMD worse, consider reducing your dose, switching to another medication or quitting altogether.
Taking iron supplements or folic acid supplements can help if your PLMD is related to an iron or folic acid deficiency.
Doctors often prescribe dopaminergic drugs, such as Carbidopa-Levodopa (Sinemet) to treat PLMD. These drugs are usually used to treat Parkinson’s disease.
If you have PLMD, benzodiazepine sleeping pills, such Triazolam (Halcion) and Temazepa) (Restoril) can help keep you from waking up during the night.
Opioids, such as Oxycodone (OxyContin) and anticonvulsant medications can also sometimes help sufferers of PLMD.
If your sleep study shows that you have obstructive sleep apnea as well as periodic limb movement disorder, treating your sleep apnea with a Continuous Positive Airway Pressure (CPAP) machine, should reduce the severity of your PLMD.
See What Happens When We Sleep and Dream? to learn more about the stages of sleep.