Pediatric Periodic Limb Movement Disorder (PLMD)
Periodic limb movement disorder (PLMD) is a condition in which children kick or jerk their legs while sleeping. Symptoms usually happen every 20 to 40 seconds and can last for a few minutes to several hours.
PLMD is often confused with restless legs syndrome (RLS) but, while the two conditions often occur together, they're not the same thing. While RLS can happen at any time, PLMD only affects sleeping patients.
Scientists still don't know the exact cause of PLMD, although it's likely due to abnormalities in the nervous system. It may also be associated with dopamine production in the brain. PLMD is more common in children with attention deficit hyperactivity disorder (ADHD) than other kids.
Although PLMD can happen in the arms, it is much more common in the toes, feet and legs. Most kids with PLMD aren't aware of the movements. Symptoms of PLMD include
- More than five unconscious limb movements in an hour
- Discomfort in the calves or thighs, either while your child is falling asleep or if he awakens during the night
- Drowsiness during the day
Tests and Diagnosis
Periodic limb movement disorder is especially hard to diagnose in kids because it sometimes takes years for specific symptoms to show up. Often, children with PLMD are described as "restless sleepers" by parents.
A pediatrician will want to know if PLMD or RLS run in your family. Parents with the condition have a 50% chance of passing it onto their kids. The doctor will also ask you about your child’s sleep history and perform a physical exam to rule out other medical conditions. A parent simply watching a child while he sleeps is not good enough for a diagnosis of PLMD. The best way to diagnose it is a sleep study (also called a polysomnogram).
During the sleep study, your child will spend the night in a sleep lab. Besides limb movements, polysomnography records eye movements, brain activity, heart rate and blood pressure. It also can tell how much oxygen is in your child’s blood and how much air is moving through her nose while she breathes.
Besides having periodic limb movement disorder (PLMD), your child may also have excessive daytime sleepiness or insomnia. If your child doesn't have the above problems, she probably won't need treatment for the PLMD at all. If it's severe, though, PLMD can interfere with your child's development or affect his grades and family or social life.
Medications should be the last option when treating a sleep disorder such as PLMD. Changing your child's sleep habits (sleep hygiene) is usually the first step in tackling any sleep disorder. Here are steps you can take at home:
- Make sure your child has a regular bedtime and nighttime routine.
- Make sure your child gets some kind of physical activity, preferably outside, every day.
- Make sure your child's bedroom is quiet, cool and dark (a small night light is fine).
- Maintain a similar sleep schedule on weeknights and weekends (staying up late and sleeping in can disrupt the body's sleep-wake cycle).
- Reserve the hour before bed as "quiet time" (no bright lights, television or computer screens).
- Avoid heavy meals within two hours of bedtime (light snacks are okay).
- Avoid caffeinated beverages in the hours before bedtime.
When to see a doctor
If you've done all of the above and your child is still having trouble concentrating during the day, see a doctor. A sleep specialist may recommend the following treatments depending on your child's symptoms:
- Iron supplementation: If your child has an iron deficiency, your pediatrician will want to bring up her iron levels. Once your child's iron stores are normal, you can supplement at home with a multivitamin. This may help some kids with PLMD.
- Medications: Clonidine and clonazepam are the most commonly prescribed medications for PLMD in children. Clonidine can aggravate sleep terrors, while clonazepam can sometimes keep kids up at night. Dopaminergic drugs that increase dopamine levels in the brain may be the safest bet in treating kids with PLMD. Talk to your doctor about the side effects and safety of any drugs. You should carefully weigh potential problems with your child's symptoms before choosing medications to treat PLMD.
How common is PLMD in children?
PLMD and RLS are common in adults, but less so in children. Between 85 and 90% of kids with RLS also have PLMD.
What causes PLMD?
The exact causes of PLMD are unknown. PLMD (and many other sleep disorders) often run in families.
How can I tell if my child has periodic limb movement disorder?
Although restless legs syndrome (RLS) and PLMD are different diagnoses, up to 85% of patients have both conditions. If your child has RLS, there's a good chance he has PLMD as well. Kids with ADHD are more likely to have PLMD, although the relationship is complicated. For instance, a lack of sleep due to PLMD may cause daytime inattention or restlessness. There also is a link between iron deficiency and PLMD.
What is the prognosis for children with PLMD?
Good sleep hygiene can help with other disorders such as insomnia that affect daytime performance. Unfortunately, there currently is no cure for PLMD.