Myoclonus is a sudden muscle jerk. It can happen on its own or as a symptom of a medical condition. Causes include side effects of medication, 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. If this is the case, a person may not require treatment.

More severe myoclonus can limit mobility and cause pain or discomfort. When the issue is a symptom of epilepsy, treatment usually involves anti-seizure medication.

Also, a doctor may, in some cases, recommend Botox injections to help prevent muscle jerks.

Below, we look into the types, causes, and treatments of myoclonus.

a persons legs in bed that are jerking around because of What to know about myoclonusShare on Pinterest
A person may experience myoclonus as a side effect of medication.

Myoclonus is the medical term for a sudden jerking of a muscle or group of muscles. This is involuntary — the person is not in control of the movement.

Muscle jerks can happen at random or in response to a trigger. They may repeat in a pattern. Myoclonus is not always serious: A hiccup is one example.

In other cases, myoclonus may 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, if there is damage or dysfunction in parts of the brain that control movement, this can result in muscle jerks.

There are many forms of myoclonus. A doctor may, for example, describe it as primary or secondary.

Primary myoclonus appears on its own, with no other symptoms. This 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 with other symptoms and may not be the most notable one.

Sleep myoclonus

This often happens as a person falls asleep. It may occur without other issues or be a symptom of restless legs syndrome.

In some people, sleep myoclonus causes discomfort and difficulty sleeping. Lifestyle changes and medication can help.

Essential myoclonus

This refers to muscle jerks with no other symptoms. It does not tend to improve or worsen, and it can run in families.

Stimulus-sensitive myoclonus

This is a reaction to movement, noise, or light. Being surprised can make a person more susceptible to these muscle jerks.

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 at the same time, 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.

Action myoclonus can result from brain damage caused by an injury.

Cortical reflex myoclonus

This type of epilepsy starts in the outer layer of the brain 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 type of epilepsy 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.

Muscle jerks may affect one muscle or a group of muscles. The movement is usually sudden and a person has no control over it.

Muscle jerks may happen singly or in quick succession, and sometimes they are triggered by specific movements or external factors such as changes in light.

If an involuntary jerk happens when a muscle contracts, the medical term for this is positive myoclonus. If it happens when a muscle relaxes, this is negative myoclonus.

Alongside myoclonus, a person may feel a trembling or twitching sensation.

People with epilepsy may experience myoclonic seizures. These involve the muscles jerking repeatedly, 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.

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:

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. It is most common to experience muscle jerks when falling asleep or waking. People with epilepsy can be more likely to experience symptoms when tired or stressed.

Some medications — including antibiotics, antipsychotics, antidepressants, and opiates — can cause myoclonus as a side effect. A doctor may recommend trying an alternate 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 massage, more exercise, adjusted sleep patterns, and cutting out alcohol from the diet.

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 is affecting daily life or it occurs with other symptoms, a doctor can recommend a range of treatment options.

Myoclonus, or sudden muscle jerks, can result from various issues. It may occur by itself or with other symptoms, and it can range from mild to severe.

Although the causes have yet to be fully explored, there is a clear link with the brain and nervous system. Research into treatments for more severe myoclonus is ongoing.