General Myoclonus

 General Myoclonus

Overview

Myoclonus is the medical term for sudden, rapid, brief, involuntary jerking of a muscle or group of muscles. These shock-like movements may be caused by sudden muscle contractions (positive myoclonus) or sudden losses of muscle tone (negative myoclonus). Many different neurological disorders can cause myoclonus; therefore, neurologists consider it a symptom of disease rather than a specific diagnosis. Indeed, everyone experiences myoclonus on occasion. For example, "sleep starts," also known as “hypnic jerks,” are the shock-like twitches that some people experience while drifting off to sleep. This is a form of myoclonus that occurs in normal, healthy individuals. Pathological myoclonus, however, may be extremely disabling.

Myoclonus may affect a small region (focal or segmental myoclonus), such as one hand, or may produce violent jerks over the entire body (generalized myoclonus). Myoclonic jerks may occur alone or in sequence, either in a pattern or randomly. When patterned, they sometimes resemble more common forms of tremor. They may occur infrequently or many times each minute. All types of myoclonus are similar insofar as the movement cannot be controlled by the person who is experiencing it and, in contrast to a tic, there is no warning or premonitory sensation. In more severe cases, myoclonus can distort movement and severely limit a person’s ability to walk, talk and eat. These types of myoclonus may indicate that an underlying condition of the brain or nerves is causing the myoclonus.

Classifying the many different kinds of myoclonus is difficult, as the causes, clinical effects, and responses to treatment vary greatly. It can be classified in a number of ways. By distribution (body parts affected), myoclonus can be classified as focal, multifocal, or generalized and by provoking factors as spontaneous and reflex. Myoclonus can also be classified on physiology, meaning, the presumed source of its origin in the nervous system: cortical (brain), subcortical (between the brain and spinal cord), spinal, or peripheral (nerves outside of the central nervous system). It is useful for physicians to classify myoclonus by physiology because the presumed source of myoclonus (cortical, subcortical, spinal, or peripheral) helps guide the physician towards the most effective treatment.

Myoclonus can occur at rest, when maintaining posture, or during action. Stimulus sensitive myoclonus is a type of myoclonus triggered by outside stimuli such as lights, noise or movement. It can be brought on by surprise as well.

SYNONYMS

No synonyms found

SUBDIVISIONS

action myoclonus

arrhythmic myoclonus

cortical myoclonus

cortical-subcortical myoclonus

dyssynergia cerebellaris myoclonica

familial arrhythmic myoclonus

hereditary essential myoclonus

infantile myoclonic encephalopathy and polymyoclonia

intention myoclonus

Lance-Adams syndrome

myoclonic epilepsy

nocturnal myoclonus

opsoclonus

palatal myoclonus

paramyoclonus multiple

pathological myoclonus

peripheral myoclonus

postanoxic intention myoclonus

postencephalitic intention myoclonus

progressive myoclonic epilepsy

respiratory myoclonus

rhythmical myoclonus

segmental myoclonus

stimulus-sensitive myoclonus

subcortical/non-segmental myoclonus

SIGNS & SYMPTOMS

There are different forms of myoclonus and they are classified in different ways. One way of classifying the different forms is by their cause. Some of the types of myoclonus are:

Physiologic myoclonus

This occurs in neurologically normal people. The occurrence of myoclonus during sleep and sleep transitions is the most common example.

Essential myoclonus

In this type, the myoclonic jerks or twitches are usually the most prominent or only clinical finding. This type of myoclonus usually progresses slowly or not at all. There are hereditary (autosomal dominant) and non-inherited, random (sporadic) forms.

Progressive myoclonus epilepsy (PME)

This is a group of diseases characterized by myoclonus, epilepsy, and other symptoms such as trouble walking or speaking. These disorders tend to get worse over time (progressive).

Sleep myoclonus

This typically occurs just at the moment of dropping off to sleep. In some cases, the affected individual does not find it particularly troublesome. In other cases, it may interfere with the sleep process. Myoclonus may be a symptom in certain sleep disorders such as restless legs syndrome.

Symptomatic (secondary) myoclonus

This is the most common category and usually is found in the setting of an identifiable underlying disorder. Myoclonus may not be the most prominent clinical symptom. Common co-existing problems include ataxia, dementia, and Parkinsonism. Myoclonus may also be a symptom associated with infections, non-neurologic medical illnesses, toxic-metabolic states, and storage diseases.

Causes

Myoclonus may be caused by a variety of underlying problems. It is commonly separated into different types based on what is causing it. The cause can help determine treatment.

Physiological myoclonus

This type of myoclonus occurs in healthy people and rarely needs treatment. Examples include:

Hiccups.

Sleep starts.

Shakes or spasms due to anxiety or exercise.

Infant muscle twitching during sleep or after a feeding.

Essential myoclonus

Essential myoclonus occurs on its own, usually without other symptoms and without being related to any underlying illness. The cause of essential myoclonus is often unknown. In some cases, the cause is hereditary, meaning passed down in families.

Epileptic myoclonus

This type of myoclonus occurs as part of an epileptic disorder.

Symptomatic myoclonus

Symptomatic myoclonus results from an underlying medical condition. It is sometimes called secondary myoclonus. Examples include:

Head or spinal cord injury.

Infection.

Kidney or liver failure.

Lipid storage disease.

Chemical or drug poisoning.

Prolonged oxygen deprivation.

Medicine reaction.

Autoimmune inflammatory conditions.

Metabolic disorders.

Coronavirus disease 2019 (COVID-19).

Nervous system conditions that result in secondary myoclonus include:

Stroke.

Brain tumor.

Huntington's disease.

Creutzfeldt-Jakob disease.

Alzheimer's disease.

Parkinson's disease and Lewy body dementia.

Corticobasal degeneration.

Frontotemporal dementia.

Multiple system atrophy.

Diagnosis

To diagnose myoclonus, your health care provider reviews your medical history and symptoms and conducts a physical examination.

You may have tests to find the cause and rule out other potential causes of myoclonus. In some cases, imaging tests or nerve tests may be needed.

Electroencephalography (EEG). This procedure records the electrical activity of the brain. It may help determine where in the brain the myoclonus originates. First, small electrodes are attached to the scalp. You then may be asked to breathe deeply and steadily and look at bright lights or listen to sounds. These actions may uncover irregular electrical activity.

Electromyography (EMG). In this procedure, electrodes are placed on multiple muscles, especially muscles that are involved in the jerking.

An instrument records the electrical activity from the muscles when they are at rest and when they are contracted, such as when you bend your arm. These signals help determine the pattern and origin of the myoclonus.

Evoked potential studies. These tests measure the electrical activity of the brain, brainstem and spinal cord that is triggered by touch, sound, sight and other stimuli.

Magnetic resonance imaging (MRI). An MRI scan may be used to check for structural problems or tumors inside the brain or spinal cord, which may cause the myoclonus symptoms. An MRI scan uses a magnetic field and radio waves to produce detailed images of the brain, spinal cord and other areas of the body.

Laboratory tests. Your health care provider may suggest genetic testing to help identify possible causes of myoclonus. Blood or urine tests may be needed to check for metabolic disorders, autoimmune disease, diabetes, and kidney or liver disease. They also can check for drugs or toxins.

Treatment

Treatment of myoclonus works bets if you can stop the problem that's causing it. For example, treatment may focus on another condition, a medicine or a toxin that is causing the myoclonus.

Most of the time, however, the underlying cause can't be cured or eliminated. In these cases, treatment is aimed at reducing myoclonus symptoms, especially when they're disabling. There are no drugs specifically designed to treat myoclonus. But treatments for other diseases may help relieve myoclonus symptoms. More than one drug may be needed to control the symptoms.

Medications

Medicines that health care providers commonly prescribe for myoclonus include:

Tranquilizers. Clonazepam (Klonopin), a tranquilizer, is the most common drug used to treat myoclonus symptoms. Clonazepam may cause side effects such as loss of coordination and drowsiness.

Anticonvulsants. Drugs used to control epileptic seizures may help reduce myoclonus symptoms. The most common anticonvulsants used for myoclonus are levetiracetam (Keppra, Elepsia XR, Spritam), valproic acid, zonisamide (Zonegran, Zonisade) and primidone (Mysoline). Piracetam is another anticonvulsant that's been found to be effective, but it's not available in the United States.

Valproic acid may cause side effects such as nausea. Levetiracetam may cause side effects such as fatigue and dizziness. Side effects from primidone may include sedation and nausea.

Therapies

OnabotulinumtoxinA (Botox) injections may help treat various forms of myoclonus, particularly if only a single area is affected. This treatment blocks the release of a chemical messenger that triggers muscle contractions.

Surgery

If myoclonus symptoms are caused by a tumor or lesion in the brain or spinal cord, surgery may be an option. People with myoclonus affecting parts of the face or ear also may benefit from surgery.

Deep brain stimulation has been tried in some people with myoclonus and other movement disorders. Electrodes are implanted within certain areas of the brain. The electrodes produce electrical signals to block the irregular impulses that can cause myoclonus. Researchers continue to study deep brain stimulation for myoclonus.

Type of Doctor Department :Neurologists