Periodic Limb Movement Disorder

Periodic limb movement disorder (PLMD) is a condition that can occur at night or during the day. PLMD causes difficulty sleeping, bedtime resistance, frequent leg jerking movements, restless sleep, and involuntary arm movement. In addition, interruption of sleep can lead to difficulty focusing during the daytime, which may present at attention deficit or hyperactivity behaviors. The good news is that periodic limb movement disorder is treatable, even though a cure does not exist at this time.

RLS vs. PLMD

What is the difference between periodic limb movement disorder and restless leg syndrome? There are many similarities between RLS and PLMS. However, the symptoms of RLS include uncomfortable leg sensations and an overwhelming urge to move the legs. These symptoms are often worse during rest and in the evening. The main difference between these two conditions is that PLMD occurs only when the person is asleep, whereas RLS happens when asleep and awake. Around 85% of people who suffer from RLS also have PLMD, but this is not true for people with only PLMD.

With PLMD, the movements are rhythmic, occurring every 20-40 seconds. However, the frequency of the movements may vary from person-to-person and from night-to-night. People with PLMD are often unaware of their condition, and experience fatigue and sleepiness during the daytime. PLMD often occurs in conjunction with restless leg syndrome (RLS).

PLMD Causes and Risk Factors

PLMD is either primary or secondary. The exact cause of primary periodic limb movement disorder is unknown. Researchers believe that it may be linked to nerve regulation. With secondary PLMD, the condition is related to medication use or another disorder. The causes include:

• Anemia
• Diabetes
• Multiple system atrophy
• Obstructive sleep apnea
• Narcolepsy
• Spinal cord injury/tumor
• Uremia
• Antidepressants
• Antihistamines
• Antipsychotics

Risk factors of PLMD are being a woman and being older. PLMD is more common in older people, affecting 35% of those 60 years of age and older. In addition, women are affected by periodic limb movement disorder twice as often as men.

Diagnosis and Testing

Periodic limb movement disorder is diagnosed using clinical history, physical examination, and testing. The doctor checks to see if there are underlying problems and takes a detailed medical history, asks about medications, and will inquire about lifestyle factors. The diagnostic test used is the overnight polysomnogram (PSG), which is carried out in a sleep lab.

In addition to the PSG test, the doctor may use blood tests to assess for conditions associated with periodic limb movement disorder. These tests include blood counts (check for anemia), electrolyte studies (assess magnesium, sodium, and potassium levels), and thyroid function tests. The doctor may have the patient complete a sleep diary 14 days before the official consultation, which details sleeping patterns and associated symptoms.

Treatment of Periodic Limb Movement Disorder

One of the main things the doctor will do is to have you avoid caffeine. Overuse of caffeine is associated with PLMD, and it also can disturb sleep. In addition, PLMD is treated by controlling underlying causes, such as anemia and diabetes. Many medications are used to treat this condition. PLMD treatment includes:

• Dopamine agonists – These agents are used as first-line for treatment of PLMD. Dopamine agonists increase the levels of dopamine, which is a brain chemical that regulates muscle movement.
• Benzodiazepines – Valium, Ativan, and Xanax can be used to suppress muscle contractions and enable the patient to rest at night.
• Anticonvulsants – These drugs will reduce muscle contractions and lessen the symptoms associated with PLMD.
• GABA agonists – These medications stop/block the release of certain brain chemicals, which will reduce muscle spasms.