What Is the Definition of Sleep Myoclonus?

Sudden jerking movement is a sign

A baby sleeping. Credit: Getty Images

What is the definition of the term sleep myoclonus? If you have ever seen your infant jerk suddenly during sleep, you may want to learn about sleep myoclonus. The condition can also affect adults, however.

Defining Sleep Myoclonus

Sleep myoclonus is a condition in which your infant has a sudden jerking movement during sleep. It may even appear like a sudden twitching in your baby.

Nocturnal myoclonus, also known as periodic limb movement disorder (PLMD), involves repetitive movements of the legs during sleep or even wakefulness.

 It usually affects both sides equally and causes a flexion of the fingers, wrists, elbows and occasionally feet. It may occur repeatedly. Sleep myoclonus happens during the early stages of sleep and it may be provoked by stimulus.

This condition may cause concern as it may seem like a seizure or infantile spasms. The important difference is that sleep myoclonus only occurs in sleep.

It often develops during the first week of life and it resolves by itself within one year. There are no adverse consequences, so it is commonly called benign neonatal sleep myoclonus. Infants who experience this will have a normal neurologic examination and EEG.

If these movements occur during wakefulness, further evaluation by your child's doctor may be necessary. Sleep myoclonus is sometimes confused with a seizure.

How Is Nocturnal Myoclonus Different from Seizures?

Although the cause is not clear, nocturnal myoclonus may involve problems with a neurotransmitter called dopamine -- this is unlike seizures, which involve electrical changes in the brain.

Myoclonus, for adults, also may result as a side effect to some drugs, including levodopa, cyclic antidepressants and bismuth salts.

The condition often improves after a patient stops taking the drug causing the problem. If you suspect this is your problem, talk to your doctor before abruptly stopping any medication, however.

In benign neonatal sleep myoclonus, the jerking movements occur during sleep and abruptly stop when the baby is awakened. It generally goes away with age. 

Other conditions with slightly different symptoms also may affect the legs and disrupt sleep. These include restless legs syndrome, periodic limb movements of sleep, night starts and nocturnal leg cramps. They may need further evaluation and treatment (except for night starts).

Can Nocturnal Myoclonus Be Treated?

If nocturnal myoclonus is disruptive to sleep, it may be treated with tetrabenazine, a drug often used to treat movement disorders such as Huntington’s disease. In one study, the condition was significantly improved over a period of five years using this drug, with drowsiness as the most significant side effect. In most cases, however, treatment is not necessary if sleep is relatively normal.

If you're suffering from sleep myoclonus or have a child or other family member who is, visit a health care provider for further evaluation. Although the condition often resolves on its own, a doctor's visit might put your mind at ease and help you rule out other conditions that might be causing the problems you're experiencing, such as restless leg syndrome.

As with any medical condition, the sooner you get treatment, the sooner you can begin taking control of your symptoms.


Coulter, DL et al. "Benign neonatal sleep myoclonus." Arch Neurol 1982; 39:191.

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