Periodic limb movement disorder (PLMD) is a sleep disorder characterized by rhythmic movements of the limbs during sleep. The movements typically involve the legs, but upper extremity movements may also occur. Movements occur periodically throughout the night and can fluctuate in severity from one night to the next. They tend to cluster in episodes that last anywhere from a few minutes to several hours. These movements are very different from the normal spasms, called hypnic myoclonia, that we often experience initially while trying to fall asleep.
What Causes PLMD?
The causes of PLMD are unknown. However recent research has shown that people with a variety of medical problems, including Parkinson's disease and narcolepsy, may have frequent periodic limb movements in sleep.
Iron deficiency seems to be the most commonly recognized cause of PLMD and its cousin, Restless Legs Syndrome. Vitamin B12, thyroid function, and folic acid and magnesium levels may be related to the disorder.
What Are the Symptoms of PLMD?
Symptoms of PLMD are usually leg movements with the extension of the big toe in combination with a partial flexing of the ankle, knee, or hip. Movement of the legs is more typical than movement of the arms. It can often cause a partial or full brief awakening, resulting in fragmented sleep. Patients are frequently unaware of these movements.
How Is PLMD Diagnosed?
A sleep partner may observe PLMD, which often affects the partner before the person knows of his or her behavior. In other cases, the diagnosis is made with the use of an overnight polysomnogram (a test that records bodily functions during sleep). This test is often used to assess the cause of daytime sleepiness or recurrent awakenings from sleep. Blood work may be done in order to test iron status, folic acid, vitamin B12, thyroid function, and magnesium levels.
How Is PLMD Treated?
If iron deficiency is found, iron supplements will be prescribed.
Generally, there are several classes of drugs that are used to treat PLMD. These include drugs closely related to those that treat Parkinson's disease, anticonvulsant medications, benzodiazepines, and narcotics. Current treatment recommendations consider the anti-Parkinson's type medications as a first line of defense. Medical treatment of PLMD often significantly reduces or eliminates the symptoms of these disorders.
There is no cure for PLMD and medical treatment must be continued to provide relief.