Myoclonus: Symptoms, Types, Causes And Treatment

The myoclonus or myoclonus are contractions or sudden jerks of a muscle or group of muscles. People who experience them cannot control these spasms, that is, they are involuntary. The term myoclonus can be divided into “mio”, which means muscle, and “clonies” or “clones” which mean “jerk.”

Both muscle contraction (called positive myoclonus) and sudden, uncontrolled muscle relaxation (called negative myoclonus) can occur in myoclonus. The latter can cause the person to fall by losing the muscle tone that kept them standing.


Its frequency also varies, and it can occur singly or many times in a short time. Myoclonus appears from a wide variety of causes, although it is also experienced by healthy people.

For example, when we have hiccups, we would be having a myoclonus. Just like when we get scared or we fall asleep and we get spasms in an arm or a leg. They are totally normal situations that do not pose any problem.

However, myoclonus in other contexts may be a symptom of disease or poisoning. In these cases, they are usually due to nervous system disorders such as epilepsy, metabolic disorders or reactions to medications. They are usually characterized by affecting more than one part of the body and occur more frequently.

In the most severe cases, myoclonus can affect balance and movement, interfering with daily activities such as walking, talking, or eating.

To control myoclonus, the best option is to treat the underlying problem. However, if the cause is unknown or cannot be specifically treated, treatment is focused on improving the patient’s quality of life.


Myoclonus occurs as muscle contractions, spasms, or jerks that are involuntary. They can appear on a single limb, or even cover the entire body. The patient may indicate that he feels an uncontrollable jolt, as if he were being given an electric shock. Myoclonus usually have the following characteristics:

– They are involuntary.

– Sudden.

– Of short duration.

– They vary in frequency and intensity.

– They can appear in the whole body or in a part.

– It can be very intense and affect activities such as walking, eating or talking.


Myoclonus are generally divided into several categories to facilitate their treatment. The types of myoclonus are:

Physiological myoclonus

This type occurs in healthy people and very rarely requires treatment. Among these is sleep myoclonus, that is, those involuntary jerks that we have when we are falling asleep.

Other examples can be hiccups, which are contractions of the diaphragm. In addition to spasms due to anxiety or physical exercise, the startle reflex (fright), as well as muscle spasms that babies have after a meal.

Essential myoclonus

This type occurs on its own, that is, without any abnormality in the central nervous system or in the nerves. This type of myoclonus is usually stable and does not intensify over time.

The cause of this type of myoclonus is generally unknown, although it could be hereditary because in some cases it recurs in the same family. Some believe it may be a form of epilepsy whose cause cannot be detected.

Action myoclonus

This is generated or intensified when the person moves voluntarily or has the intention to move. This type of myoclonus is one of the most serious.

It can affect the limbs and the face, causing great disability. It is usually due to a lack of oxygen or blood in the brain.

Palatine myoclonus

It is a rapid and regular contraction of the soft palate. Most cases occur in adults and have an indefinite duration. Affected people may feel a clicking sound in the ear when contraction occurs.

Progressive myoclonic epilepsy

It is a set of epilepsies that are characterized by myoclonus in various parts of the body. They are accompanied by generalized tonic-clonic seizures (due to altered electrical activity throughout the brain). As well as visual hallucinations and progressive neurological degeneration. Difficulty walking and speaking is also usually observed.

Juvenile myoclonic epilepsy 

It is a type of epilepsy that usually appears in adolescence. It is characterized by episodes of intense shaking mainly in the upper limbs.

It is one of the most common types of epilepsy, and it can appear in 1 individual in every 1000. These patients respond very well to treatment, disappearing in more than 80% of cases.

Cortical reflex myoclonus

They are considered a type of epilepsy that affects the cerebral neocortex, that is, the outermost layer of the brain . It usually only occurs in specific muscles in the body, although it can cover many muscles. Apparently, its appearance is facilitated by certain movements or sensations.

Reticular reflex myoclonus

Apparently it is a type of epilepsy that occurs in the brainstem . Contractions are normally seen throughout the body, affecting both sides of the body equally. It can arise both from a voluntary movement and from the appearance of an external stimulus.

Stimulus-sensitive myoclonus

These appear by sudden external stimuli such as lights, noise or movement. This is common in photosensitive epilepsy.

Opsoclonus-myoclonus syndrome

It is a very rare neurological disorder that is characterized by rapid eye movements called opsoclonos, as well as myoclonus, lack of coordination, irritability and fatigue. Its cause usually consists of tumors or viral infections.

Secondary or symptomatic myoclonus

This type of myoclonus occurs as a consequence of an underlying condition. Some examples are Parkinson’s, lesions in the central nervous system, tumors, or Huntington’s disease. Some more are described in the next section.


It is not known exactly what causes the myoclonus. In general, myoclonus occurs when altered electrical impulses reach a muscle or a group of muscles.

These impulses come from the cerebral cortex, the brainstem, or the spinal cord. However, they can also arise from nerve damage (in the peripheral nervous system ).

There are a wide variety of conditions that are associated with myoclonus. Some of them are:

– Epilepsy.

– Brain or spinal cord injuries.

– Stroke (cerebrovascular accident).

– Brain tumors.

– Hypoxia (brain lesions that appear due to lack of oxygen for a long period of time).

– Huntington’s disease.

– Multiple sclerosis.

– Myoclonus can be an early symptom of Creutzfeldt-Jakob disease.

– Alzheimer disease.

– Parkinson’s disease, due to the degeneration of the basal ganglia , which are involved in movement.

– Lewy body dementia.

– Corticobasal degeneration.

– Frontotemporal dementia.

– Multiple systemic atrophy.

– Genetic conditions.

– Liver or kidney failure.

– Intoxication by chemicals, drugs or drugs. Some examples are heavy metals, methyl bromide, levadopa, carbamazepine, opioids, or tricyclic antidepressants (in high doses).

– Infections.

– Metabolic disorders. For example, hyperglycemia or hypoglycemia (very high or very low blood sugar levels), lack of magnesium or sodium.


Myoclonus are generally detected by reviewing the patient’s medical history and performing a physical examination. An electroencephalography (EEG) may also be needed to record electrical activity in the brain and determine which area is causing these changes.

On the other hand, an electromyography (EMG) is also recommended. This test measures the electrical activity of the muscles, observing the characteristics of the myoclonus and its origin.

Magnetic resonance imaging (MRI) is useful to see if there are structural problems in the brain or spinal cord that are causing the myoclonus.

Laboratory tests such as blood or urine tests are used to detect the presence of drugs or toxins, metabolic disorders, diabetes, or kidney or liver disease.


The efficacy of treatment depends on the possibility of determining the underlying cause of the myoclonus, and whether it is reversible. In this way, treating the origin of the problem, myoclonus would be interrupted.

However, in most cases, the exact causes cannot be detected. Therefore, treatment is aimed at alleviating symptoms and improving the patient’s quality of life.

Tranquilizing medications such as clonazepam are generally used to treat myoclonus. However, this drug has multiple side effects such as drowsiness or loss of coordination.

Anticonvulsants such as levetiracetem, valic acid, and primidone are also used. These medications also have side effects such as nausea, dizziness, or fatigue.

Other therapies used are botox injections in the affected areas. This is useful when there is a specific area where myoclonus occurs, since the chemical messengers that generate muscle contractions are blocked.

In cases where myoclonus occurs as a result of a brain tumor or injury, surgery may be recommended.

Recently, deep brain stimulation is being used. It is a surgically implanted neurostimulator that transmits electrical signals to areas of the brain that control movement. Its goal is to block the abnormal nerve stimuli that myoclonus produces.


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