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Sleep Disorders and Periodic Limb Movement Disorder

Introduction to PLMD

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.

PLMD may be caused by medications, most notably, antidepressants.

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 affect the partner before the patient knows of his or her behavior. In other cases, the diagnosis is made on 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.

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