Myoclonus is a sudden muscle jerk. It can happen alone or stem from a medical condition. Possible causes include medication side effects, damage to the nervous system, and disorders that affect the brain.
In some people with myoclonus, the jerks are mild and have little or no effect on daily life. In these cases, treatment might not be necessary.
More severe myoclonus can limit mobility and cause pain or discomfort. When the muscle jerks are a symptom of epilepsy, the treatment usually involves anti-seizure medication. For other causes, doctors may recommend Botox injections as a preventive treatment.
This article discusses the types of myoclonus, its causes, and the treatment options.
What is myoclonus?
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Myoclonus is the medical term for a sudden jerking of a muscle or group of muscles. The jerking is involuntary, meaning that the person is not in control of the movement.
Muscle jerks can happen at random or in response to a trigger, and they may repeat in a pattern. Myoclonus is not always serious — for example, it can present as hiccups or hypnic jerks.
However, it can sometimes be a symptom of an underlying health condition, such as epilepsy. It can also be a response to injury, infection, or poisoning.
The exact causes are still unclear. However, damage to or dysfunction in parts of the brain that control movement can result in muscle jerks.
Types of myoclonus
There are many forms of myoclonus, and a doctor may describe the condition as primary or secondary.
Primary myoclonus appears on its own with no other symptoms. It can develop in various parts of the body, including the legs and the roof of the mouth. Among the many possible causes are injury, illness, and poisoning.
Secondary myoclonus is a symptom of an underlying medical condition, such as Parkinson’s disease or restless legs syndrome. It appears alongside other symptoms, which may be more significant than the muscle jerks.
Sleep myoclonus
Sleep myoclonus often happens as a person falls asleep, as well as during sleep. It may occur without other issues or be a symptom of restless legs syndrome.
In some people, sleep myoclonus causes discomfort and difficulty sleeping. Proper sleep hygiene and medication can help.
Essential myoclonus
Essential myoclonus refers to muscle jerks with no other symptoms.
The National Institute of Neurological Disorders and Stroke (NINDS) notes that it does not tend to improve or worsen over time. Although the cause can sometimes be unknown, the condition seems to run in families, so genetics likely plays a role.
Stimulus-sensitive myoclonus
Stimulus-sensitive myoclonus refers to muscle jerks that happen as a reaction to movement, noise, or light.
A person may be more susceptible to these muscle jerks if the stimulus is unexpected.
Palatal myoclonus
Palatal myoclonus involves the muscles in the roof of the mouth contracting very quickly in a regular rhythm.
Muscles in the tongue, throat, and face may jerk simultaneously, and the issue can cause pain or discomfort.
Action myoclonus
This severe form of myoclonus can cause jerking in the face, arms, and legs when a person tries to move. It often worsens when a person is trying to make precise movements, such as picking up a pen.
Brain damage resulting from an injury can cause action myoclonus.
Cortical reflex myoclonus
This is a type of epilepsy that starts in the brain’s outer layer and usually affects specific muscles in one part of the body.
It can cause muscle jerks that worsen when the person tries to make a specific movement.
Reticular reflex myoclonus
This is another type of epilepsy that involves the brain stem. It causes muscle jerks that can affect the whole body.
Changes in noise and light can be triggering. A person may also find that trying to make specific movements triggers the jerks.
Progressive myoclonus epilepsy
Other symptoms of this type of epilepsy include seizures, difficulty speaking, and mobility challenges. They usually worsen over time.
Progressive myoclonus epilepsy can be fatal.
Myoclonus symptoms
According to NINDS, the symptoms of myoclonus can include:
- Muscle jerks: They may affect one muscle or a group of muscles.
- Sudden movements: The movement is usually sudden, and a person has no control over it.
- Occurrence: Muscle jerks may happen singly or in quick succession.
- Triggers: Specific movements or external factors, such as changes in light, can trigger them.
Muscle jerks can be due to positive or negative myoclonus. Positive myoclonus is the medical term for when an involuntary jerk happens as a muscle contracts. Negative myoclonus is when a jerk happens as a muscle relaxes.
Alongside myoclonus, a person may feel a trembling or twitching sensation.
People with epilepsy may experience myoclonic seizures. These involve the muscles repeatedly jerking in quick succession for a few seconds. The most commonly affected areas are the upper arms, shoulders, and neck.
A person is usually fully awake and alert during a myoclonic seizure.
What triggers myoclonus?
Some people with myoclonus will experience involuntary movements after a trigger.
According to a 2021 article, triggers can include:
- some auditory, tactile, or visual stimuli
- movement
- strong emotions or feelings, such as stress
It is worth noting that some people have no obvious triggers for their myoclonus.
Many people who have epilepsy experience myoclonus. Epilepsy affects electrical signals in the brain, and sudden surges in electrical activity cause muscle jerks, seizures, and the loss of awareness for short periods.
Triggers can vary among people with epilepsy, but they may include being tired or stressed.
Myoclonus causes and risk factors
Myoclonus can occur with no other symptoms and no obvious cause. A person may experience mild myoclonus as a lifelong condition.
It can run in families, so genetics likely plays a role.
Also, damage to the brain or nervous system can cause myoclonus. The damage may result from:
- a stroke
- a head or spinal cord injury
- a brain tumor
- liver or kidney failure
- oxygen deprivation
- poisoning
Myoclonus can develop as a symptom of other medical conditions, including:
- Parkinson’s disease
- Creutzfeldt-Jakob disease
- multiple sclerosis
- Alzheimer’s disease and other types of dementia
- autoimmune encephalitis
Drugs that cause myoclonus
Certain drugs can also cause myoclonus. A 2017 study found evidence that a very wide variety of medications may have the potential to cause myoclonus in some people.
Drugs that may be especially likely to do so include the following:
- opioids
- antidepressants
- antipsychotics
- antibiotics
More research is necessary on this topic so that doctors can have the most reliable information possible about myoclonus-causing drugs.
Treatment and management for myoclonus
Some medications — including antibiotics, antipsychotics, antidepressants, and opioids — can cause myoclonus as a side effect. A doctor may recommend trying an alternative drug if this is the case.
Anti-seizure drugs that treat epilepsy can relieve myoclonus.
If a person experiences mild myoclonic seizures, which last for a few seconds, they may not need treatment.
If medication is ineffective, a doctor may recommend Botox injections to relieve the muscle jerks, as Botox causes muscles to relax.
If myoclonus is a symptom of restless legs syndrome, medication and some lifestyle changes can help. A person may benefit from:
- getting a massage
- doing more exercise
- adjusting their sleep patterns
- refraining from drinking alcohol
Myoclonus vs. clonus
Myoclonus is a sudden and involuntary jerky movement, which can arise for many different reasons.
Clonus is also a kind of involuntary movement, but scientists define it specifically as a stretch reflex that is rhythmic and oscillating. Damage to the upper motor neurons causes these involuntary rippling movements, although researchers continue to debate the exact causes.
Myoclonus vs. dystonia
As a recent article explains, dystonia is another condition that leads to involuntary movements.
In particular, people with dystonia experience muscle contractions that lead to twisting, abnormal posturing, and repetitive motions.
The severity can vary among individuals. Some people with dystonia need assistance to perform all everyday activities.
Frequently asked questions
Below, we answer some common questions about myoclonus.
Is myoclonus a seizure?
Myoclonus is not a seizure, although some people have conditions that cause seizures and myoclonus. The most common of these is epileptic myoclonus.
Can myoclonus kill you?
There is no evidence that myoclonus itself can be fatal.
However, myoclonus may indicate the presence of conditions that can be life threatening, such as multiple sclerosis or Parkinson’s disease. For this reason, doctors will want to determine the underlying cause of myoclonus.
When to speak with a doctor
It is advisable to see a doctor after experiencing myoclonus for the first time. The doctor will perform a physical examination and check for underlying health issues.
If myoclonus affects daily life or occurs alongside other symptoms, the doctor can recommend a range of treatment options.
Summary
Myoclonus is the term for sudden muscle jerks, and it has several types and various causes. It may occur by itself or with other symptoms and can range from mild to severe.
Although researchers have yet to explore the causes fully, there is a clear link with the brain and nervous system. Research into treatments for more severe myoclonus is ongoing.
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