Myoclonus

Overview

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

Other forms of myoclonus may occur because of a nervous system disorder, such as epilepsy, a metabolic condition, or a reaction to a medicine.

Treating whatever condition causes myoclonus can help control symptoms. Sometimes the cause of myoclonus is unknown or can't be specifically treated. In these cases, the goal of treatment is to reduce the effects of myoclonus on quality of life.

Symptoms

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

Sudden
Brief
Involuntary
Shock-like
Variable in intensity and frequency
Occurring in one part of the body or all over the body
Sometimes severe enough to interfere with eating, speaking or walking

When to see a doctor

If your myoclonus symptoms become frequent and persistent, talk to your health care provider about a diagnosis and treatment options.

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.

Preparing for an appointment

You'll probably first discuss your concerns with your primary care provider. Your provider might then refer you to a neurologist. A neurologist is a specialist trained in nervous system conditions.

Because appointments can be brief, and because there's often a lot to talk about, it's a good idea to arrive well prepared for your appointment. 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.
Take a list of all your medicines, including any vitamins or supplements.
Write down questions to ask your health care provider, asking about possible causes, treatments and prognosis.

Your time with your health care provider is limited, so preparing a list of questions ahead of time will 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?
Other than the most likely cause, what are other possible causes for my symptoms?
What kinds of tests do I need?
Is my condition likely temporary or chronic?
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 health care provider is likely to ask you a number of questions. Being ready to answer them may make time to go over any points you want to discuss in-depth. You might be asked:

When did you first start having symptoms?
Do you have a history of seizures or other neurological conditions?
Have you been exposed to drugs or chemicals?
Do you have a family history of myoclonus or epilepsy?
Have your symptoms been continuous or occasional?
How severe are your symptoms?
Does anything improve your symptoms?
What, if anything, appears to worsen your symptoms?