Periodic Limb Movement Disorder

Periodic Limb Movement Disorder (PLMD) is characterized by repetitive limb movements that occur while sleeping or lying awake (mostly the lower legs), involving brief muscle twitches, and an upward dorsi-flexion of the foot, knee or hip. It is considered abnormal when more than 5 or more involuntary movements per hour of sleep occur, with each limb movement lasting 0.5 to 5 seconds in duration.

PLMD may be found in children and adults. Its occurrence increases with age and is particularly common in the elderly, affecting 35% of people aged 65 and older.

Although you may not aware of these limb movements, your quality of sleep is often compromised and your bed partner might recognize them. These frequent limb movements can disrupt your sleep and may cause you or your bed partner to have insomnia, restless sleep, or excessive daytime sleepiness. Although periodic limb movements during sleep (PLMS) are typically seen in patients with restless legs syndrome (RLS), patients with periodic limb movement disorder (PLMD) by definition do not have RLS symptoms. The cause of PLMD remains unclear. It shares some similarities with RLS. Similar medications can manage both disorders. Low iron level can exacerbate RLS and PLMD as well as some anti-nausea medications and most antidepressants.

WHEN SHOULD YOU SUSPECT PLMD?

You may or may not be aware of your symptoms, which makes it harder for you to know if leg movements may be present during sleep. However, the following symptoms may alert you or your bed partner. 

1. Do you have repetitive and intermittent limb movements while asleep?

2. Are your bed sheets a mess or untidy in the morning or do you feel you have had restless sleep at night?

3. Do you feel fatigued or sleepy even though you had a full night sleep?

Consequences 

Like any sleep disorder, PLMD may affect your ability to maintain adequate restorative sleep and cause excessive daytime sleepiness. When you suffer from a sleep loss, you are more prone to fatigue, increased illness, impaired task performance, decreased memory, short attention span, altered mood, depression or anxiety. Consult one of our providers, especially if the symptoms adversely affect your quality of sleep, daytime functioning, or worsen with age.

Diagnosis

The diagnosis of RLS is primarily based on the patient’s history, followed by an examination to identify secondary causes such as iron deficiency anemia. Your may undergo testing to rule out an iron deficiency. Keep a sleep diary to record your sleep quality or quantity as well as when your symptoms occur and their severity. If deemed necessary, you may be asked to undergo an overnight sleep study (polysomnogram) to rule out other sleep disorders such as obstructive sleep apnea that may worsen RLS.

Treatment

If another underlying disorder such as obstructive sleep apnea causes your symptoms, your provider will address it so as to decrease the severity of your symptoms. If necessary, you may be prescribed a medication that is also used to treat RLS. Treatment is administered according to the severity of the symptoms, the level of relief experienced with the medication, and any potential side effects experienced by the patient.