Myoclonus

On this page

What is myoclonus?

Myoclonus is a type of uncontrollable movement that includes sudden, brief involuntary twitching, jerking, or spasm of a single muscle or a group of muscles. A person experiencing myoclonus cannot control it. Myoclonus is the word for the movements themselves. It is not a disease itself, but may be a sign of another neurological condition.

Causes of myoclonic twitches or jerks are:

Sudden muscle contractions (tightening), called positive myoclonus
Sudden muscle relaxation, called negative myoclonus

Myoclonus usually happens from a disruption of the brain or spinal cord. It can also happen after an injury to the peripheral nerves (nerves outside of the brain and spinal cord).

People may notice a pattern of movement in the jerks or twitches, or they may appear random. Myoclonus can happen only once in a while, or many times in a minute. Sometimes, a person trying to make a conscious movement may trigger myoclonus.

Types of myoclonus

The two general types of myoclonus are:

Physiologic myoclonus, which happens in otherwise healthy people and doesn’t need medical treatment. Some examples are hiccups and the jerks (or “sleep starts”) that some people have while drifting off to sleep.
Pathologic myoclonus, which happens because of an underlying disorder of the brain or nerves. It can also be a sign of another medical condition, or a reaction to certain types of medicine. It usually involves more persistent and severe symptoms which may limit a person’s ability to eat, talk, or walk.

It can be difficult to figure out what’s causing or triggering myoclonus, but some common experiences in myoclonus include:

Stimulus-sensitive myoclonus, which is triggered by various external events, including noise, movement, light, or being surprised.
Sleep myoclonus (also known as hypnic myoclonus), which happens during sleep and sleep transitions, often as a person is drifting off to sleep.
Essential myoclonus, which happens on its own and is not caused by abnormalities in the brain or nerves. It is usually stable and doesn’t get worse over time, or progresses very slowly.
Action myoclonus, which is triggered by voluntary movement or even a person’s intention to move. It may get worse when the person tries to make precise, coordinated movements.
Epileptic myoclonus, which happens within an epilepsy syndrome. Some examples of syndromes with myoclonic seizures include:
- Juvenile myoclonic epilepsy (JME) starts around puberty and involves myoclonic seizures, usually of the neck, shoulders, or upper arms. It also involves generalized seizures (affecting the whole body).
- Myoclonic-astatic epilepsy involves myoclonus followed by a loss of muscle tone.
- Lennox-Gastaut Syndrome happens in childhood and involves multiple seizure types that are usually difficult to control, as well as cognitive impairment.
- Progressive myoclonus epilepsy (PME) is a group of rare disorders that involve myoclonic seizures and other neurologic symptoms such as trouble walking or speaking. These disorders often get worse over time and sometimes are fatal. One of its many forms is Lafora body disease (also known as Lafora progressive myoclonus epilepsy), which includes myoclonic seizures, progressive loss of memory, and difficulty with intellectual functions.
Benign neonatal sleep myoclonus (BNSM) is a condition that affects newborn babies. Newborns with this condition will have sudden, jerky movements of their limbs or bodies in their sleep. This condition is harmless and about 95% of cases go away by 6 months of age.
Palatal myoclonus (also known as palatal tremor) is a regular, rhythmic contraction of one or both sides of the rear of the roof of the mouth (soft palate). The contractions are fast and may continue during sleep. The condition usually appears in adults and sometimes does not go away. People with palatal myoclonus may note a “clicking” sound in the ear when the muscles in the soft palate contract.
Middle ear myoclonus involves uncontrolled muscle movements of the tensor tympani, a muscle in the ear, causing repetitive clicking, cracking, or thumping sounds. Usually, the tensor tympani tightens to protect the inner ear (like placing a hand on the top of a drum to dampen the sound). The muscle movement usually happens when the person talks, eats, coughs, laughs, or makes other sounds with their mouth. It is harmless and can be treated with surgery or other treatments.
Opsoclonus myoclonus (OMS) (also known as Dancing Eyes-Dancing Feet Syndrome or Kinsbourne syndrome) is a rare disorder that affects the eyes and muscles and causes other problems. In young children, it is most often caused by a tumor called neuroblastoma that triggers the immune system to attack the nervous system by mistake. In adults, the condition is most often related to lung or breast cancers. It can also happen on its own or after a bacterial or viral infection. People with OMS may have irregular, rapid eye movements, jerking muscles in the arms or legs, poor coordination, hand tremor, difficulty speaking, eating, walking, or sleeping, behavioral changes, and decreased muscle tone.

Myoclonus can also be categorized based on where the movement starts in the nervous system.

Cortical myoclonus starts in the cerebral cortex (the outer layer of the brain). In this type, myoclonic jerks usually involve only a few muscles in one part of the body, usually in the limbs, but jerks involving many muscles also may happen. It becomes more intense when a person tries to move in a certain way (action myoclonus) or in response to sensory stimulation (stimulus-sensitive myoclonus).
Reticular reflex myoclonus starts in the brainstem (the part of the brain that controls vital functions such as breathing). Myoclonic jerks usually affect the whole body, mimicking a startle reflex. It can also be triggered by a person’s movement or surroundings.
Spinal myoclonus begins in the spinal cord. It can involve muscle groups controlled by one or more connected parts of the spinal cord, called segmental myoclonus. Sometimes, the myoclonic jerk involves the whole torso, beginning in the middle of the spine and spreading up and down. This is known as propriospinal myoclonus.

Peripheral myoclonus refers to myoclonic jerks that come from a peripheral nerve (nerves outside of the brain and spinal cord). One example is hemifacial spasm (muscle spasms on one side of the face).

Who is more likely to get myoclonus?

Myoclonus can happen by itself or as a symptom of a wide variety of nervous system disorders. For example, myoclonic jerks may develop in people with multiple sclerosis or epilepsy. They may also develop in people with neurodegenerative diseases, such as:

Involuntary twitches or spasms can happen in people with no family history of myoclonus and with no known cause (known as idiopathic). But it also can appear among members of the same family—suggesting that it runs in families. In some families, essential myoclonus is associated with essential tremor or dystonia (myoclonus-dystonia).

Myoclonus may also happen with infection, head or spinal cord injury, stroke, brain tumors, kidney or liver failure, chemical or drug intoxication, lipid storage diseases, autoimmune inflammatory conditions, COVID-19, or metabolic disorders. Prolonged oxygen deprivation to the brain (hypoxia) may lead to post-hypoxic myoclonus. Some genetic disorders, such as Krabbe disease and Wilson disease, can cause myoclonus.

Studies suggest that myoclonus usually begins in the cerebral cortex. However, scientists don’t yet fully understand the specific factors that cause myoclonus. They believe some types of stimulus-sensitive myoclonus may involve overexcitability of the parts of the brain that control movement. Laboratory studies suggest that an imbalance between chemicals called neurotransmitters may cause myoclonus.

How is myoclonus diagnosed and treated?

Diagnosing myoclonus

After reviewing a person’s medical history and a physical exam, a doctor may order the following tests to confirm a diagnosis of myoclonus:

Electromyography (EMG) to measure electrical activity of muscle
Electroencephalography (EEG) to record the electrical activity in the brain that may trigger the myoclonic jerk
Evoked potential studies to capture the electrical activity in the brain, brainstem, and spinal cord in response to specific stimuli (sounds, touch, visuals)
Urine or blood tests to look at possible causes, rule out other conditions—such as metabolic disorders, diabetes, autoimmune disease, and kidney or liver disease—that may cause symptoms similar to myoclonus, and to check for drugs or toxins
Magnetic resonance imaging (MRI) to produce three-dimensional images of the brain, spinal cord, nerve, and other tissue (including muscles)
Genetic testing to find possible causes.

Learn more about neurological diagnostic tests and procedures.

Treating myoclonus

There are no medications designed to specifically treat myoclonus, but medications that reduce an overactive nervous system are generally used to relieve symptoms. Sometimes, treatments for other conditions a person has can relieve or control myoclonus symptoms. Some medications have a limited effect when used by themselves, but have a greater effect when combined with other medicines. Several treatments are available to help treat myoclonus:

Clonazepam, a type of tranquilizer, is the most commonly used medication to treat myoclonus.
Antiepileptic drugs such as levetiracetam, valproic acid, and zonisamide are used to treat myoclonus. Certain antiepileptics such as phenytoin, carbamazepine, lamotrigine, and vigabatrin are best avoided in cortical myoclonus, as they may actually make myoclonus worse.
Botulinum toxin (commonly known as Botox®) injections can reduce excess muscle activity by blocking muscle contraction at the cellular level. It is the first-line therapy for hemifacial spasm and has been effective in treating some people with palatal myoclonus.
Surgery may be an option if myoclonus symptoms result from a tumor or lesion in the brain or spinal cord, or if the condition affects parts of the face or ear.
Deep brain stimulation has been performed in some people with myoclonus. Electrodes are implanted in certain areas of the brain and produce electrical signals that block the irregular impulses causing myoclonus.
Immunotherapies can be used for OMS treatments, including corticosteroids or the hormone ACTH, intravenous immunoglobulin therapy, plasmapheresis, rituximab, or cyclophosphamide. Some people recover fully, while others continue to show symptoms. Some may have a relapse of neurological symptoms.

Certain psychiatric medications, antiepileptics, or cardiac medications can cause myoclonus. Tell your healthcare provider if you notice myoclonus after starting a new medication. Also, make sure to manage health conditions like kidney or liver diseases and other chronic conditions that can cause myoclonus.

What are the latest updates on myoclonus?

The National Institute of Neurological Disorders and Stroke (NINDS), a part of the National Institutes of Health (NIH), is the leading federal funder of research on the brain and nervous system, including myoclonus. As part of its mission, NINDS conducts and funds research on myoclonus and other related disorders. In addition to NINDS, other NIH institutes and centers fund research on movement disorders, including myoclonus.

Biomarkers are measurable indicators of disease that can sometimes help predict the progression and severity of a disease. The Juvenile Myoclonic Epilepsy Connectome Project (JMECP) aims to define biomarkers of JME. Using state-of-the-art imaging methods, NINDS-funded researchers measure altered structural and functional connections between brain regions in people ages 12 to 20 who are living with JME. Results may lead to new clinical tools for diagnosis and personalized management.

Animal models are used to study the mechanisms involved in myoclonus. Using an animal model, the researchers are trying to understand how chemical imbalances in the nervous system happen, leading to myoclonus and other abnormal movements. For example, NINDS-funded scientists have developed a mouse model of myoclonus-dystonia. They found that motor symptoms improve with alcohol consumption. Researchers tested the hypothesis that abnormal activity of the cerebellum causes myoclonus and dystonia in myoclonus-dystonia, and that alcohol injections normalize cerebellar activity by acting on targets in the cerebellum to relieve motor symptoms. Results may provide a better understanding of the underlying cause of myoclonus-dystonia and provide targets for treatment options.

Researchers are also trying to develop new therapies for neurological disorders that can cause myoclonus. Glycogen storage disease is a group of rare conditions that happens when a person’s body does not properly process glycogen, which is a source of stored energy. Lafora disease is one of these conditions which causes myoclonic epilepsy as well as cognitive impairment. NINDS-funded researchers are developing therapies to help degrade or break down Lafora bodies, which are abnormal clumps in the cell. In pre-clinical trials with mice, NINDS-funded researchers of the Lafora Epilepsy Cure Initiative developed therapeutic agents against Lafora body disease and myoclonus epilepsy. Another NINDS-funded study will develop an Early Diagnosis Campaign to prepare a group of people with early-stage and moderately advanced Lafora body disease for human clinical trials. The study will identify clinical biomarkers of disease progression.

People can be affected by more than one movement disorder, such as myoclonus and dystonia, myoclonus and parkinsonism, or myoclonus and tremor, which makes diagnosis and treatment challenging. NINDS-funded researchers are recruiting research participants with familial and sporadic complex movement disorders to identify genetic mutations and biological mechanisms that may cause these disorders. Findings may lead to improvements in disease diagnosis and treatment.

Botulinum toxin is a treatment for a variety of movement disorders. A NINDS study compared the use of ultrasound and electrophysiologic guidance (using electrical stimulation and a needle) to precisely target muscles for botulinum toxin injection. Researchers hope to treat upper limb spasticity and focal hand dystonia, which feels like muscle stiffness and tightness in the arms and hands, and muscle spasms in the hand. Results may lead to improved treatment for movement disorders like myoclonus.

More information about myoclonus research may be found using NIH RePORTER, a searchable database of current and past research projects supported by NIH and other federal agencies. RePORTER also has links to publications and resources from these projects.

For research articles and summaries on myoclonus, search PubMed, which contains citations from medical journals and other sites.

How can I or my loved one help improve care for people with myoclonus?

Clinical trials increase our understanding of SPS and related disorders with the goal of improving how doctors treat them. Consider participating in a clinical trial so clinicians and scientists can learn more about myoclonus. Clinical research with human participants helps researchers learn more about a disorder and perhaps find better ways to safely detect, treat, or prevent disease.

All types of participants are needed—those who are healthy or may have an illness or disease—of all different ages, sexes, races, and ethnicities to ensure that study results apply to as many people as possible, and that treatments will be safe and effective for everyone who will use them.

For information about participating in clinical research visit NIH Clinical Research Trials and You. Learn about clinical trials currently looking for people with myoclonus at Clinicaltrials.gov, a searchable database of federal and private clinical studies.

Where can I find more information about myoclonus?

Information may be available from the following resources:

MedlinePlus

National Organization for Rare Disorders (NORD)
800-999-6673