Myoclonus

Overview

Myoclonus refers to a quick jerking movement that you can't stop from happening. Hiccups and the sudden jerks or "sleep starts" that you may feel just before falling asleep are forms of myoclonus. These movements occur in otherwise healthy people and usually aren't serious.

Other forms of myoclonus may be due to a nervous system condition, such as epilepsy. Jerking movements also can result from a metabolic condition or a reaction to a medicine.

Treating the condition that causes myoclonus can help manage symptoms, but sometimes the cause isn't known. When this happens, the goal of treatment is to reduce the effects of myoclonus on quality of life.

Myoclonus can appear in different patterns, and specialists group these patterns into types to help describe what the jerking movements look like and what may be causing them. An updated classification system gives a clearer way to organize these types and guide care.

Newer ways of classifying myoclonus

Experts recently updated how myoclonus is grouped and described. This helps care teams talk about the condition in a clearer, more consistent way and gives a better framework for choosing tests and treatments.

Why an update was needed

Older labels such as essential, epileptic or symptomatic myoclonus are still helpful, but they don't fully capture the many different ways myoclonus can appear or what causes it. As testing methods have improved, specialists needed a system that reflects what is now known.

What's new

The updated approach looks at myoclonus from two angles:

1. What the jerking movements look like. This includes:

   • Where they happen on the body.
   • What brings them on, such as movement, sound, touch or rest.
   • How strong or frequent they are.
   • What simple nerve and muscle tests show.

   This helps the care team understand how the jerks are being generated in the nervous system.

2. What is causing the jerking movements. This includes:

   • Genetic conditions.
   • Metabolic or chemical imbalances.
   • Infections or inflammation.
   • Structural changes in the brain or spinal cord.

Looking at both the features and the possible causes gives a clearer overall picture.

How this helps in care

This system is already being used by neurologists and movement disorder specialists. It supports more-accurate diagnosis and helps guide next steps, such as which tests may be most helpful and which treatments may be appropriate.

You may not hear the technical terms during a visit with your healthcare professional, but the updated system helps the care team describe myoclonus in a more organized and consistent way behind the scenes.

Symptoms

People with myoclonus often describe their symptoms as jerks, shakes or spasms that are:

• Sudden.
• Brief.
• Not voluntary.
• Shocklike.
• Variable in how often they happen and how serious they are.
• In one part of the body or all over the body.
• Sometimes serious enough that they affect how people eat, speak or walk.

When to see a doctor

If your myoclonus symptoms become frequent and lasting, talk to your healthcare professional about a diagnosis and treatment options.

Causes

Myoclonus can happen for many different reasons. Some cause-related categories can help describe why the jerking movements occur and guide treatment options.

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 an illness. The cause is often not known. Sometimes essential myoclonus is passed down in families, known as a genetic trait.

Epileptic myoclonus

This type of myoclonus occurs as part of a brain condition that causes seizures, known as epilepsy.

Symptomatic myoclonus

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

• Head or spinal cord injury.
• Infection, including coronavirus disease 2019 (COVID-19).
• Kidney or liver failure.
• Lipid storage disease.
• Medicine reaction or chemical poisoning.
• Long-term reduction in oxygen levels.
• Autoimmune inflammatory conditions or metabolic conditions.

Nervous system conditions that result in secondary myoclonus include:

• Stroke.
• Brain tumor.
• Huntington's disease.
• Creutzfeldt-Jakob disease.
• Alzheimer's disease, frontotemporal dementia or Lewy body dementia.
• Parkinson's disease.
• Corticobasal degeneration.
• Multiple system atrophy.

Risk factors

Risk of myoclonus is higher in people who have nervous system conditions. This includes epilepsy, Parkinson's disease, Huntington's disease and others. It also can occur in people with other conditions, such as an infection, a brain tumor or a spinal cord injury. Essential myoclonus can run in families, so your risk is higher if a family member has it.

Diagnosis

To diagnose myoclonus, your healthcare professional reviews your medical history and symptoms and gives you a physical exam.

You may have tests to look for the cause of your symptoms. Imaging tests or nerve tests also may be needed.

• Laboratory tests. Blood or urine tests can check for metabolic conditions, autoimmune diseases, diabetes, and kidney or liver disease. They also can look for signs that toxins or medicines are the cause of your symptoms. Your healthcare professional also may recommend genetic testing.

• Electroencephalography (EEG). This procedure records the electrical activity of the brain. It may help determine where in the brain your symptoms begin. Small metal discs called 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 help your healthcare professional find irregular electrical activity.
• Electromyography (EMG). In this procedure, electrodes are placed on multiple muscles, especially muscles involved in the jerking movements. 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 changes or tumors inside the brain or spinal cord, which may cause 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.

Treatment

Treatment of myoclonus works best if you can address the cause. For example, treatment may focus on another condition, a medicine or a toxin that is causing symptoms.

Most of the time, the cause can't be cured or eliminated. Treatment is aimed at reducing symptoms, especially when they're disabling. There are no medicines designed to treat myoclonus, but treatments for other diseases may help relieve your symptoms. More than one medicine may be needed.

Medicines

Medicines that healthcare professionals commonly prescribe for myoclonus include

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

• Antiseizure medicines. These medicines can help reduce myoclonus symptoms. The most common antiseizure medicines used are levetiracetam (Keppra, Spritam), valproic acid, zonisamide (Zonegran, Zonisade) and primidone (Mysoline). Piracetam is another medicine 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 fatigue and dizziness. Side effects from primidone may include sedation and nausea.

Therapies

OnabotulinumtoxinA (Botox) injections may help treat various forms of myoclonus, especially 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 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. They produce electrical signals to block the irregular impulses that can cause myoclonus. Researchers continue to study deep brain stimulation for myoclonus.

Preparing for an appointment

You're likely to see your healthcare professional. Your health professional might then refer you to a specialist trained in nervous system conditions, called a neurologist.

Here's some information to help you get ready for your appointment and to know what to expect.

What you can do

• Be aware of any pre-appointment restrictions, and ask if there's anything you need to do in advance.
• Write down a list of your symptoms, noting if there's anything that seems to trigger them or make them better.
• Make a list of all your medicines, including any vitamins or supplements, and doses.
• Write down questions to ask your healthcare professional, including questions about possible causes and treatments.

Your time with your healthcare professional is limited, so preparing a list of questions ahead of time may help you make the most of your time together. For myoclonus, some basic questions to ask include:

• What's the most likely cause of my symptoms? Are there other possible causes?
• What kinds of tests do I need?
• Is my condition likely short term or long lasting?
• What is the best course of action?
• What are the alternatives to the primary approach that you're suggesting?
• I have other health conditions. How can I best manage them together?
• Are there any restrictions that I need to follow?
• Are there any brochures or other printed material that I can take home with me? What websites do you recommend visiting?

In addition to the questions that you've prepared, don't hesitate to ask questions during your appointment at any time that you don't understand something.

What to expect from your doctor

Your healthcare professional is likely to ask you a number of questions. You might be asked:

• When did you first start having symptoms?
• Do you have a history of seizures or other nervous system conditions?
• What medicines do you take?
• Have you taken illegal drugs or been exposed to chemicals?
• Do you have a family history of myoclonus or epilepsy?
• Have your symptoms been constant or do they come and go?
• How bad are your symptoms?
• Does anything improve your symptoms?
• What, if anything, appears to worsen your symptoms?