What is Periodic Limb Movement Disorder?

ADC Sleep Disorders Center

What is PLMD?

Periodic limb movement disorder (PLMD) is similar to RLS in many ways. It is associated with night-time limb movement complaints, reduced sleep quality and problems with daytime functioning. Unlike RLS patients, people with PLMD do not complain about the “creepy-crawly” feelings or the “overwhelming urge to move.”

Instead, individuals with PLMD have uncontrolled leg kicks that are reported by their bed partner or recorded on a sleep study. When the leg kicks are seen on a sleep study they are called periodic limp movements of sleep (PLMS).

PLMS usually occur in the legs but may also affect the arms. As the name implies, the movements are periodic. They occur over and over, usually every 30 seconds. They typically consist of a movement of the big toe, together with an upward bending of the ankle, knee or hip. The movements are often called jerking or kicking. They usually do not occur throughout the entire night. Most PLMS occur in the first half of the night.

If your sleep study shows periodic leg movements 5 or more times during each hour of your sleep, they may e serious enough to prevent you from sleeping. You may wake up often during the night due to your leg movements, but not realize it is from the leg movements. When this happens, you may complain of difficulty falling and/or staying asleep.

The PLMS may cause brief awakenings many times during the night. Some people may not be aware of these awakenings. This often leads to a feeling of poor sleep quality. Patients with PLMS may fall asleep during the day, while reading, watching TV, working or driving.

PLMS may cause several other problems, some of which may affect your bed partner and some of which affect you. Your bed partner may complain of being kicked at night, of the bed covers being twisted or knocked off the bed or that limp movements shake the bed. You may notice that the frequent leg movements are wearing hair off your legs.

Your doctor may want to confirm a diagnosis of PLMD. This requires PLMS on a sleep study and complaints of daytime effects. Although patients with RLS often have PLMS, PLMS are not required to have the diagnosis of RLS. Thus, you can only have PLMD if you do not have RLS or another disorder that causes leg movements at night (such as sleep apnea).

How common are PLMS and PLMD?

PLMS becomes more common with age. PLMS is rarely seen in people younger than 30 years of age. PLMS affects a small percentage of people age 30-50; one-third of people age 50-65; and almost half of people over age 65. Men and women are equally likely to be affected. However, most people have PLMS only. Experts agree that PLMD is quite rare.

What causes PLMS/PLMD?

PLMS are often seen when older patients have overnight sleep studies. PLMS are associated with several common medical conditions including: neuropathy, spinal cord diseases, kidney disease, rheumatologic disorders, narcolepsy, obstructive sleep apnea and REM sleep behavior disorder. Some antidepressant medications can also increase the frequency of PLMS. Studies have suggested that some of the same factors associated with RLS, such as heredity and iron deficiency, may also be associated with the development of PLM as well as PLMD.

How are PLMS/PLMD diagnosed?

An overnight sleep study is needed to make the diagnosis of PLMD. Small electrodes will be taped to your legs and/or arms to record movements at night. They overnight study also helps to rule out any other sleep disorders including sleep apnea.

How are PLMS/PLMD treated?

Some patients with PLMD sleep lightly and are easily disturbed by the movements (PLMS). They may be able to reduce or eliminate their sleep complaints by improving the soundness of their sleep.

(Learn how to improve sleep quality in our blog, “How Do I Get Better Sleep?”)

 

Learn more about PLMS and PLMD or schedule an appointment at ADC’s Sleep Disorder Center.

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