What Is Sleep Myoclonus?

It may seem as though infants have cornered the market on the move: A quick shudder, followed by complete stillness, that occurs while they're sleeping.

Some adults are known to joke that the child must be having a "baby dream." It's a happier thought than the fear it could be a seizure.

You may be able to relate to these "sleep starts." Just as you're drifting off to sleep, you suddenly jolt awake.

There's a name for this sudden movement. It's called myoclonus, which the National Institutes of Health defines as a "brief, involuntary twitching or jerking of a muscle or group of muscles." Hiccups are a form of myoclonus.

When it happens during sleep, it's called sleep myoclonus. It's more common in childhood but can linger through adulthood. Most of the time, sleep myoclonus is perfectly normal and is nothing to worry about.

This article discusses the symptoms, causes, and types of myoclonus. It also addresses treatment, which is necessary only if the myoclonus interferes with sleep and diminishes quality of life.

Symptoms

The symptoms of sleep myoclonus are difficult to miss. In addition to twitching and jerking, the signs might also be called shakes, spasms, or contractions. And they can happen in all sorts of ways: once or many times in a row, a single episode or many times a night, in a pattern or not.

The symptoms are similar in that they are:

• Brief
• Involuntary
• Localized to one part of the body or all over the body
• Shock-like
• Sudden
• Involuntary
• Variable in intensity and frequency
  

Causes

Although the cause is not entirely clear, sleep myoclonus may involve problems with a neurotransmitter, or brain chemical, called dopamine. This distinction alone differentiates it from seizures, which involve electrical changes in the brain.

Myoclonus may be a side effect of some drugs, including levodopa (a treatment for Parkinson's disease), tricyclic antidepressants, and bismuth salts (used for treating heartburn, nausea, and upset stomach). The condition often improves once the drug is stopped.

Many types of myoclonus (not just sleep myoclonus) are usually triggered by one of the following:

• A blip in the central nervous system (namely, the brain or spinal cord)
• Multiple sclerosis, epilepsy, or a neurodegenerative disease such as Parkinson’s disease or Alzheimer’s disease
• A brain tumor, stroke, kidney or liver failure, or a head or spinal cord injury

If a physician can identify the underlying problem, they will be in a better position to recommend a treatment—if one is necessary at all.

Types of Myoclonus

Of the various types of myoclonus, the first is so common and harmless that it usually doesn't require any type of treatment. It's called physiological myoclonus, and it looks like that twitching infant.

Other common types of myoclonus are:

• Epileptic myoclonus, which is common among people who live with epilepsy
• Essential myoclonus, which is often unrelated to an illness and sometimes hereditary
• Sleep myoclonus, which may or may not occur alongside restless legs syndrome
• Symptomatic myoclonus, which is spawned by an underlying medical condition such as the ones listed above

Sleep Myoclonus In Children

Myoclonus is a condition that may worry parents when it occurs in children as it may seem like a seizure or infantile spasms. The important difference is that sleep myoclonus occurs only in sleep.

Infants who experience sleep myoclonus should have a neurologic examination and electroencephalogram (EEG), a test that measures electrical activity in the brain. If these movements occur during wakefulness, further evaluation by your child's doctor may be needed to rule out seizures and other causes.

Treatment

Sleep myoclonus is not considered serious or in need of treatment unless it interferes with sleep and/or someone's quality of life.

If it does, the condition may be treated with Xenazine (tetrabenazine), a drug often used to treat movement disorders such as Huntington’s disease.

In most cases, however, treatment is not necessary if sleep is relatively normal. Sleep myoclonus is widely referred to as a "benign" condition, meaning that it has no short- or long-term effects on health or well-being for the affected individual.

Summary

Myoclonus is a "brief, involuntary twitching or jerking of a muscle or group of muscles." Hiccups are a form of myoclonus. With sleep myoclonus, this twitching or jerking occurs during sleep.

A "blip" in the central nervous system may cause myoclonus, or it may be triggered by an underlying medical condition. Sleep myoclonus doesn't usually require treatment unless it interferes with sleep. If it occurs while an infant or child is awake, further testing might be needed to check for epilepsy or other issues.

A Word From Verywell

If you're suffering from sleep myoclonus or have a child or other family member who is, visit a healthcare 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, such as restless legs syndrome. As with any medical condition, the sooner you get treatment, the sooner you can begin taking control of your symptoms.