Sleep myoclonus is involuntary, nonrhythmic muscle twitching that occurs either as a person falls asleep or during sleep.

Sleep myoclonus is not a disease but a symptom of several different conditions. Sleep myoclonus can also happen without a known cause.

In this article, we discuss what sleep myoclonus is, its causes, and how doctors treat it.

What is it?

The term myoclonus refers to involuntary spasms that involve a muscle or group of muscles. A hiccup is a type of myoclonus affecting the muscles of the diaphragm.

The symptoms of sleep myoclonus occur when a person falls asleep or during sleep. It causes unpredictable and involuntary muscle jerks or spasms that may affect a single muscle or multiple muscle groups.

These movements may include:

• sudden jerking of the arms, legs, or torso
• shock-like muscle twitches that last for a brief period
• localized or widespread muscle spasms
• muscle spasms that occur in response to external stimuli

There are two types of myoclonus: positive and negative. Positive myoclonus involves muscle contractions, whereas negative myoclonus involves muscle relaxation and loss of muscle tone.

Simple forms of myoclonus, such as hiccups or sleep starts, can occur in healthy people without leading to serious complications. However, frequent or widespread myoclonus may indicate an underlying neurological disorder.

People with sleep myoclonus may have difficulty falling asleep or experience poor sleep quality, which can lead to excessive daytime fatigue.

Causes
The exact cause of myoclonus remains unknown. However, in most cases, myoclonus is associated with problems affecting the brain or spinal cord.

Sleep myoclonus can occur by itself or alongside other symptoms of nervous system disorders.

The possible causes of sleep myoclonus vary depending on a person’s age.

Infants and children
Causes of sleep myoclonus in children may include:

Sleep disorders
Although sleep myoclonus can occur on its own, it can also occur as a symptom of a sleep disorder.

Pediatric periodic limb movement disorder
Pediatric periodic limb movement disorder (PLMD) is a sleep movement condition that affects children. PLMD causes brief muscle spasms in the legs or arms during sleep.

Rhythmic movement disorder
Children with rhythmic movement disorder (RMD) may exhibit rocking or head jerking movements while falling asleep or transitioning to deep sleep.

RMD often occurs alongside developmental disorders, such as attention deficit hyperactivity disorder (ADHD), autism spectrum disorders, and Tourette’s syndrome.

Epilepsy
According to the National Institutes of Health (NIH), myoclonus frequently occurs in people with epilepsy.

Juvenile myoclonic epilepsy (JME) is a form of epilepsy that involves myoclonic seizures. It accounts for 5–10% of all cases of epilepsy. The onset of JME symptoms usually occurs in children between the ages of 12 and 18 years.

In adults
Causes of sleep myoclonus that mainly affect adults include:

• Restless leg syndrome
• Restless leg syndrome (RLS), or Willis-Ekbom disease, is a disorder that affects sleep. It causes an uncontrollable urge to move the legs, usually because of an uncomfortable sensation, which moving temporarily eases. It typically happens in the evening or nighttime hours when a person is sitting or lying down awake.

The nature of its symptoms suggests that RLS is a neurological condition. However, the cause of RLS remains unknown.

Research from the NIH suggests that dysfunctional basal ganglia may lead to RLS. However, genetics may play a role in early onset RLS, which appears in people before the age of 40 years.

Multiple sclerosis (MS)
According to the National MS Society, focal and segmental myoclonus are common movement disorders associated with MS.

It is unclear whether MS can directly cause sleep myoclonus. However, the condition has links with numerous sleep disorders, including nocturnal leg spasms and RLS.

Huntington’s disease
People with Huntington’s disease may experience involuntary muscle jerks, known as chorea, as well as changes in cognition and sleep.

As the disease progresses, involuntary muscle movements may start affecting a person’s sleep. According to a 2019 review, myoclonus, periodic limb movements, and RLS are relatively common conditions among people with Huntington’s disease.

In older adults
People aged 60 years or older may develop sleep myoclonus due to:

Alzheimer’s disease
In addition to cognitive changes, people with Alzheimer’s disease may experience loss of coordination and motor control.

According to a 2017 study, people with Alzheimer’s disease have an increased risk for seizures and myoclonus. The authors of the study found that people with Alzheimer’s disease developed myoclonus about 5.4 years, on average, after disease onset.

Parkinson’s disease
Parkinson’s disease is a neurodegenerative disorder that typically affects people around the age of 70 years. The symptoms include:

• tremor, or uncontrollable shaking
• muscle rigidity or stiffness
• bradykinesia, which refers to the slowing of automatic muscle movements
• loss of coordination
• changes in posture

People who have Parkinson’s disease may also have urinary and bowel problems, cognitive changes, and difficulty sleeping.

Creutzfeldt-Jakob disease (CJD)
CJD is a progressive brain disorder that leads to cognitive and behavioral changes, as well as involuntary muscle jerks and loss of coordination.

According to the NIH, symptoms of CJD typically first appear in adults aged 60 years or older. The exact cause of CJD remains unknown.

Treatment
Treating any underlying condition that contributes to myoclonus will help alleviate unwanted muscle spasms. If the cause is unknown, a doctor will treat the symptoms as they appear.

Examples of medication that can help treat sleep myoclonus include:

• antiseizure and anticonvulsant medications, such as clonazepam (Klonopin), phenytoin (Dilantin), and levetiracetam (Keppra)
• sedatives, such as barbiturates
• 5-hydroxytryptophan, an amino acid in serotonin
• botulinum toxin (Botox)
• Home remedies

The research on alternative therapies for myoclonus is limited. However, stretching and massaging problematic areas of muscle may help prevent mild muscle spasms or reduce the severity of moderate-to-severe spasms.