What to Know About Sleep Myoclonus

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Sleep myoclonus is defined as a “brief, involuntary twitching or jerking of a muscle or group of muscles.” It typically occurs as a person is falling asleep or during sleep.

It's more common in childhood but can linger through adulthood. Newborn hiccups are a form of myoclonus. Most of the time, sleep myoclonus is perfectly normal and 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.

Causes of Sleep Myoclonus
Verywell / Emily Roberts

What Are the Symptoms of Sleep Myoclunus?

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

Sleep myoclonus occurs during the early stages of sleep, especially at the moment of dropping off to sleep. It may be triggered by external stimuli such as noise, movement, or light.

What Are the Causes of Sleep Myoclunus?

Some known causes are more likely to affect certain age groups. For example, one possible cause is Parkinson's, a disease that usually manifests after age 60.

However, the exact cause of sleep myoclonus is not entirely clear, although researchers have a few theories. One primary theory has to do with sleep atonia, the natural process in which your muscles become paralyzed as you fall deeper into sleep.

During sleep atonia, brain signals that activate movements when you are awake begin to snooze for the night. It's not always a smooth transition, though. Occasionally, a brain signal volleys with electricity, resulting in a muscle spasm.

Adults

Some forms of myoclonus are experienced by all age groups, like sleep myoclonus and hiccups. Other forms of myoclonus are caused by underlying conditions that predominately affect adults, or by medications that adults are more likely to use.

Myoclonus in adults may be triggered by:

  • Drugs: The use of certain drugs can trigger myoclonus as a side effect. Drugs that most frequently cause myoclonus include opiates, antidepressants, antipsychotics, and antibiotics.
  • Stroke: An adult can develop myoclonus after a stroke that damages a nerve pathway in the brain.
  • Neurological disease: Myoclonus may develop as a symptom of multiple sclerosis, Parkinson's disease, dementia with Lewy bodies, Alzheimer's disease, celiac disease, and more.
  • Trauma: An injury to the brain, spinal cord, or elsewhere in the nervous system that damages a nerve pathway can trigger myoclonus.
  • Kidney (renal) or liver failure: Myoclonus may manifest in people with renal failure or liver failure, due to the manner in which these conditions damage muscles and nerves.
  • Infection: Certain infections that affect the nervous system can trigger myoclonus, including herpes simplex virus and Lyme disease.
  • Cancer: Some forms of cancer are associated with myoclonus, including leukemia and lymphoma, neuroblastoma (a form of brain cancer), and lung, ovarian, and breast cancers.

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.

What Is Restless Leg Syndrome?

Restless leg syndrome is a disorder that causes a person to experience a strong, uncontrolled urge to move their legs. This feeling can go away soon afterward or immediately upon experiencing the urge, but there are minor differences in how it feels between people. It has been observed to occur with sleep myoclonus.

Children

In infants, benign (non-threatening) sleep myoclonus manifests as repetitive twitches in the arms, legs, or torso while the infant sleeps.

Although research on myoclonus condition in infants is limited, researchers believe it is harmless. Nonetheless, without testing the infant's brainwaves, it is difficult to tell if the infant is experiencing myoclonus or epilepsy. Epilepsy is diagnosed with a brainwave test called electroencephalography (EEG).

Other causes of myoclonus in children include:

  • Fever or infection: Children can develop episodes of abrupt myoclonus after having a fever or infection. In cases like this, myoclonus typically resolves on its own.
  • Tumor: Neoblastoma is the most common type of malignant tumor in children seven years and younger. Approximately 2% to 3% of children with neoblastoma develop opsoclonus–myoclonus syndrome (OMS), which causes loss of coordination, tremors (often in the hands), and an inability to walk or sit.
  • Trauma: A brain or spinal cord injury can also trigger myoclonus in children if it damages the nervous system. Brief episodes of myoclonus may begin immediately after the injury and often resolve abruptly on their own.

Types of Myoclonus

There are two types of myoclonus: positive and negative myoclonus. Positive myoclonus happens when muscles abruptly contract. Negative myoclonus happens when muscles that are contracting suddenly stop.

There are numerous forms of myoclonus:

  • Action myoclonus is triggered by a movement you make or an intention to move, typically affecting the arms, legs, and face. It can be caused by brain damage due to a lack of oxygen, or happen as a symptom of another underlying neurological condition.
  • Cortical myoclonus, which is one of the most common forms of myoclonus, typically affects the upper limbs and face. Corticol myoclonus may be positive, negative, or both at the same time.
  • Epileptic myoclonus is common among people who live with epilepsy. It can happen as one component of a seizure, or on its own in the absence of a seizure. It typically happens in children with epilepsy.
  • Essential myoclonus is myoclonus which may be the primary symptom of an underlying illness, the only symptom of an underlying illness, or idiopathic (unrelated to illness). It tends to be chronic.
  • Myoclonus-renal failure syndrome is an extremely rare form of myoclonic epilepsy. Its symptoms may begin as early as age nine and progressively worsen, eventually leading to end-stage kidney failure.
  • Palatal myoclonus is slow, rhythmic muscle contractions that can happen while asleep or awake, typically affecting the eyes, face, tongue, larynx (voice box), and the intercostal muscles between the ribs.
  • Peripheral myoclonus rhythmic or sporadic jerking movements caused by a nerve injury or a lesion (i.e., a lipoma or other benign tumor) in a peripheral nerve, root nerves, or plexus nerves.
  • Propriospinal myoclonus originates in the spine and may involve the neck, waist, knees, and hips, but not the face. It typically occurs in a lying down position, sometimes during the transition between wakefulness and sleep. It is more common in middle-aged men, and may be related to spinal, trauma, tumor, or infection.
  • Startle syndrome is abrupt, rapid body jerking that happens when you are surprised by a sudden stimulus, such as a loud noise. It is normal and persists throughout life.
  • Symptomatic myoclonus is spawned by a variety of underlying medical conditions, including Parkinson's, infection, kidney failure, hyperthyroidism, and even vitamin E deficiency.

How Is Sleep Myoclonus Diagnosed?

To diagnose the cause of myoclonus, the first things your healthcare provider will consider are:

  • Your age
  • Your medications, if any
  • Whether you have recently fallen, been in a car accident, or experienced any other injuries
  • Family history

Your provider will ask you about the tremors or spasms you experience. They may ask which body part seems to be affected, how frequently the myoclonus occurs, and how long the episodes seem to last. They may also ask if you are experiencing any other new or unusual symptoms.

Depending on this information, your provider may recommend one or more of the following tests:

  • Electroencephalogram (EEG): Small discs (electrodes) are placed on your scalp to track your brainwaves for patterns that can reveal where the myoclonus starts.
  • Electromyography (EMG): Tiny needles through your skin and into your muscles to check the health of your muscles and the nerves that control them.
  • Magnetic resonance imaging (MRI): An MRI machine takes detailed images of your organs and tissues using magnetic fields and radio waves. MRIs do not involve radiation.
  • Blood test: Your provider may order a blood test to check for signs of increased immune system activity, which can point to infection and other illnesses.

How Is Sleep Myoclonus Treated?

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 the health or well-being of the affected individual.

When to See a Healthcare Provider

The occasional muscle jerk as you're drifting off to sleep is nothing to be concerned about. However, if the myoclonus is disrupting your sleep or happening while you are awake, see your healthcare provider for an evaluation.

You should also see a healthcare provider if:

  • The myoclonus happens persistently or frequently or is increasing in frequency
  • The myoclonus interferes with eating, speaking, walking, or other activities
  • You are experiencing a new type of myoclonus
  • You have any other new or unusual symptoms, including signs of infection or signs of epilepsy

Call 911 or go to the nearest urgent care if you if you experience any signs of epilepsy, including:

  • Changes in consciousness
  • Weakness
  • Visual auras, such as flashes of light or tunnel vision
  • Auditory (hearing) auras, such as ringing, buzzing, or distorted sounds
  • Somatosensory auras, like tingling or a feeling of moving despite being still
  • A metallic taste in your mouth
  • A sudden sense of impending doom

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.

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Verywell Health uses only high-quality sources, including peer-reviewed studies, to support the facts within our articles. Read our editorial process to learn more about how we fact-check and keep our content accurate, reliable, and trustworthy.
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By Brandon Peters, MD
Brandon Peters, MD, is a board-certified neurologist and sleep medicine specialist.