Myoclonus
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.
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.
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.
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 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.
References
- Aminoff NJ, et al., eds. Movement disorders associated with general medical diseases. In: Aminoff’s Neurology and General Medicine. 6th ed. Elsevier; 2021. https://www.clinicalkey.com. Accessed Oct. 10, 2022.
- Srinivasan J, et al., eds. Myoclonus. In: Netter’s Neurology. Elsevier; 2020. 3rd ed. https://www.clinicalkey.com. Accessed Oct. 10, 2022.
- Jankovic J, et al., eds. Diagnosis and assessment of Parkinson disease and other movement disorders. In: Bradley and Daroff’s Neurology in Clinical Practice. 8th ed. Elsevier; 2022. https://www.clinicalkey.com. Accessed Oct. 10, 2022.
- Ferri FF. Myoclonus. In: Ferri’s Clinical Advisor 2023. Elsevier; 2023. https://www.clinicalkey.com. Accessed Oct. 10, 2022.
- Myoclonus fact sheet. National Institute of Neurological Disorders and Stroke. https://www.ninds.nih.gov/myoclonus-fact-sheet. Accessed Oct. 10, 2022.
- Caviness JN. Classification and evaluation of myoclonus. https://www.uptodate.com/contents/search. Accessed Oct. 10, 2022.
- Caviness JN. Treatment of myoclonus. https://www.uptodate.com/contents/search. Accessed Oct. 10, 2022.
- Rabano-Suarez P, et al. Generalized myoclonus in COVID-19. American Academy of Neurology. 2020; doi:10.1212/WNL.0000000000009829.
- Deep brain stimulation. Dorland’s Medical Dictionary Online. https://www.dorlandsonline.com. Accessed Nov. 5, 2022.
- Nimmagadda R. Allscripts EPSi. Mayo Clinic. July 6, 2022.
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