Periodic Limb Movement Disorder – PLMD

Periodic Limb Movement Disorder

Also called: PLMD


Periodic limb movement disorder (PLMD) is a condition that causes patients to unconsciously flex or jerk their legs and arms during sleep. The movement may sporadically awaken the patient, which can lead to insomnia or severe daytime sleepiness.

PLMD is marked by characteristic movements that occur during sleep. Patients tend to upwardly flex the big toe, as well as the ankle, knee or hip as often as every 20 seconds. A patient’s legs may also uncontrollably twitch, jerk or kick while sleeping. Some patients may also move their arms. These flexes may occur over a few minutes to several hours.

The cause of PLMD is unknown, although it may be related to abnormalities in the patient’s brain stem or in levels of the neurotransmitter dopamine. When it occurs on its own, the disorder is more prevalent in patients older than 40 and those with poor sleep hygiene (conditions that promote sleep). PLMD may also occur in conjunction with other conditions, such as restless leg syndrome, Parkinson’s disease, narcolepsy and attention deficit hyperactivity disorder. Patients may also develop the condition when taking medications that affect dopamine levels.

A sleep study is necessary to confidently diagnose PLMD. While the patient sleeps, an electroencephalogram records the electrical activity of the brain through electrodes placed on the skin. In addition, laboratory personnel observe the sleeping patient’s limb movements.

Medications are available to treat PLMD, although treatment is typically only necessary if it causes insomnia. There is no cure for PLMD, but sedatives and dopaminergics (drugs that simulate the behavior of dopamine) tend to ease PLMD symptoms. The medications must be used regularly for proper treatment of the disorder. Because the causes of PLMD are largely unknown, it is not always possible to prevent the condition, although some behavioral changes may help.

About periodic limb movement disorder

Periodic limb movement disorder (PLMD) is a type of sleep disorder. While asleep, patients with the disorder unconsciously flex joints in the legs and less frequently in the arms. This can cause patients to repeatedly awaken, and lead to insomnia and/or daytime tiredness.

PLMD was originally named nocturnal myoclonus, and was thought to be related to epilepsy. It was later renamed PLMD because the movements are slower than those related to myoclonus (a condition characterized by jerky, involuntary muscle contractions). PLMD differs from other movement disorders in that it occurs only during sleep. PLMD is also sometimes known as periodic leg movement while sleeping (PLMS). When it causes a patient to awaken from sleep, it is sometimes referred to as periodic leg movement while waking (PLMW).

The prevalence of PLMD is uncertain, although the National Sleep Foundation estimates that 35 percent of adults 65 and older experience the condition. PLMD appears to affect men and women equally.

PLMD may occur on its own or in conjunction with other conditions. It is often associated with restless leg syndrome (RLS), which produces irritating sensations in the legs while resting or sleeping. It is estimated that more than 80 percent of patients with RLS also have PLMD, according to the National Institute of Neurological Disorders and Stroke (NINDS). However, the reverse is not true. Patients with PLMD are not necessarily more prone to experiencing RLS. According to the American Association for Respiratory Care, only 30 percent of patients with PLMD also have RLS.

PMLD has been linked to abnormalities in the brain stem, which regulates consciousness and arousal. It may also result from changes in levels of dopamine, a neurotransmitter that is typically involved in regulating balance and movement. In some cases, PLMD may indicate the presence of certain medical conditions (e.g., diabetes, anemia, kidney disease).

Risk factors and causes of PLMD

Periodic limb movement disorder (PLMD) is an idiopathic condition, which means that its cause is unknown. It may occur in conjunction with other conditions, but it may also occur on its own.

Certain conditions have been associated with PLMD. Patients with these conditions may have an increased risk of developing PLMD. These conditions include:

  • Restless leg syndrome
  • Parkinson’s disease
  • Attention deficit hyperactivity disorder (ADHD)
  • Other sleep disorders (e.g., narcolepsy, obstructive sleep apnea, REM sleep behavior disorder)
  • Kidney disease
  • Spinal cord injury

There are several additional risk factors that may increase a patient’s risk of developing PLMD, including:

  • Age. The occurrence of PLMD increases after the age of 40, with a large number of cases occurring among those 65 and older.
  • Family history. There is some evidence that similar disorders (e.g., restless leg syndrome) may be related to inherited genetic mutations. Therefore, PLMD may be more likely to occur in patients who have family members with the disorder.
  • Poor sleep hygiene. Certain behaviors and conditions are likely to reduce a patient’s overall ability to sleep and may increase the risk of developing PLMD. These include consuming alcohol, tobacco or caffeine close to bedtime. Engaging in strenuous exercise and intense mental activity in the late evening may also lead to PLMD.

In addition, certain medications are believed to induce or increase the likelihood of PLMD. Treatments with antidopaminergic, dopaminergic, or tricyclic antidepressants or cessation of barbiturates or benzodiazepines that change the concentration of the neurotransmitter dopamine  may initiate PLMD as well. Other medications may also worsen a patient’s PLMD, including lithium (often used to treat bipolar disorder) and some anti-nausea drugs.

Signs and symptoms of PLMD

Periodic limb movement disorder (PLMD) causes patients to move their legs and arms during sleep. Movements are most likely to occur during the non-REM (rapid eye movement) sleep, which occurs early in the patient’s sleep period.

PLMD-related movements range from flexing a joint to flailing the arms and legs. A characteristic movement is the upward extension of the big toe every 20 to 40 seconds over a period of a few minutes to several hours. How often the movement occurs may differ, with estimates ranging from every 10 to 60 seconds. These movements may also be accompanied by flexing of the ankle, knee or hip. A patient’s legs may uncontrollably twitch, jerk or kick while asleep. In some patients, the arms are also involved. The amount of movement typically varies from night to night.

Patients with PLMD are often unaware of their movements. In some cases, the movement causes the patient to awaken, but in many it only causes semi-arousal. This can lead to limited rest at night and daytime sleepiness and fatigue.

Diagnosis methods for PLMD

Patients with periodic limb movement disorder (PLMD) are unlikely to know what is occurring during sleep unless alerted by a bed partner. They most often visit a physician with complaints of daytime sleepiness or insomnia.

A physician will likely perform a review of the patient’s medical history, a physical examination and a neurological examination. The medical history will include a review of the patient’s symptoms, including any witnessed by the patient’s bed partner. The neurological exam typically tests the patient’s reflexes, coordination and mental status. It helps eliminate epilepsy and similar conditions as possible causes of the patient’s symptoms.

Blood tests are also often performed. These measure the body’s amounts of circulating iron, folic acid, vitamin B12, thyroid hormones and magnesium. The results help the physician rule out other possible causes of the patient’s insomnia or fatigue.

Urine tests may also be recommended to identify whether certain medications or illicit drugs could be causing the patient’s symptoms. To confirm a suspected case of PLMD, the physician is likely to request a polysomnogram. It is a type of sleep study that records the body’s electrical signals during sleep and requires an overnight stay at a sleep laboratory. During this study, an electroencephalogram (EEG), which involves electrodes that remain on the patient’s skin, is used to detect abnormal electrical activity in the patient’s brain while they sleep. Laboratory personnel will also observe the patient while asleep to record their movements.

Treatment and prevention of PLMD

Treatment for periodic limb movement disorder (PLMD) is typically not necessary unless the patient experiences severe insomnia or daytime sleepiness. When needed, treatment focuses on reducing the patient’s symptoms. However, there is no cure for the disorder.

Medications used to treat PLMD include dopaminergics (drugs that help to increase dopamine levels in the brain), sedatives and anticonvulsants. These medications may allow normal sleep, but must be used regularly for relief.

Because the causes of PLMD are largely unknown, it is not always possible to prevent the disorder. Certain behavioral changes may help reduce the occurrences of PLMD. Patients may wish to keep a daily log of diet, habits or activities, which may help identify those factors that appear to exacerbate a patient’s PLMD.

Proper sleep hygiene may help prevent or reduce the occurrence of PLMD attacks. Sleep hygiene is behavior that promotes sleep. For example, reducing caffeine consumption (e.g., from chocolate, coffee, tea and soft drinks) may help reduce PLMD occurrence. In addition, the patient’s ability to sleep may be improved by avoiding alcohol, tobacco, naps and strenuous exercise.

If possible, patients with PLMD should avoid certain medications (e.g., tricyclic antidepressants) that may make the disorder worse. However, patients are encouraged to consult their doctor before discontinuing any of their medications. A physician can help a patient determine whether the benefits of drugs such as antidepressants outweigh the risks.

Questions for your doctor regarding PLMD

Preparing questions in advance can help patients to have more meaningful discussions with healthcare professionals regarding their condition. Patients may wish to ask their doctor the following periodic limb movement disorder (PLMD)-related questions:

  1. What is periodic limb movement disorder?
  2. What causes the disorder?
  3. What are the symptoms of the disorder?
  4. Will the symptoms get worse over time?
  5. How can you test me for the disorder?
  6. How is the disorder treated?
  7. Will treatment cure the disorder?
  8. How can the disorder affect other aspects of my health?
  9. Is periodic limb movement disorder related to other movement disorders like restless leg syndrome?
  10. My child has attention deficit hyperactivity disorder. Should he also be treated for periodic limb movement disorder?
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