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Myoclonus happens very quickly and often without warning. The normal and essential forms of it aren’t preventable.
Myoclonus refers to sudden, brief involuntary twitching or jerking of a muscle or group of muscles. The twitching cannot be stopped or controlled by the person experiencing it. Myoclonus is not a disease itself, rather it describes a clinical sign.
Myoclonic jerks may occur in the following scenarios:
- Either alone or in sequence, in a pattern of movement or without pattern
- Infrequently or many times per minute
- In response to an external event or when a person attempts to make a movement
Types of myoclonus
Myoclonus can be broadly categorized into two types:
- Physiologic myoclonus involves quick muscle twitches followed by relaxation. Examples are hiccups and the jerks or “sleep starts” that some people experience while drifting off to sleep. This form occurs in healthy people, causes no difficulties, and does not require medical treatment.
- Pathologic myoclonus may involve persistent, shock-like contractions in a group of muscles and is more widespread in general. They contractions begin in one region of the body and spread to muscles in other areas. More severe cases can affect movement and severely limit a person’s ability to eat, talk, or walk. This can be one of many signs indicating a wide variety of underlying disorders in the brain or nerves, secondary to certain medical conditions, or can be a reaction to certain types of medication.
Classifying myoclonus is difficult because the causes and responses to therapy vary widely. Some of the commonly described types are:
- Stimulus-sensitive myoclonus, which is triggered by various external events, including noise, movement, and light. Being surprised may increase the sensitivity of the individual.
- Sleep myoclonus (also known as hypnic myoclonus) occurs during sleep and sleep transitions, often as one is drifting off to sleep. Some forms appear to be stimulus sensitive. While some people may not be troubled by this or need treatment, others may require treatment where myoclonus may be a symptom of a more complex and disturbing sleep disorder.
- Essential myoclonus occurs on its own and is not influenced by abnormalities in the brain or nerves. Involuntary twitches or spasms can occur in people with no family history of the condition, and the cause may be unexplained (idiopathic). However, it also can appear among members of the same family—indicating that it may be an inherited disorder. It tends to be stable without increasing in severity over time. In some families there is an association of essential myoclonus with essential tremor or a form of dystonia (myoclonus-dystonia). Dystonia is a movement disorder in which sustained muscle contractions cause twisting and repetitive movements or uncomfortable postures.
- Action myoclonus is triggered by voluntary movement or even the intention to move. It may become worse during attempts at precise, coordinated movements. It can be the most disabling form of myoclonus affecting the arms, legs, and face. One of the causes may be brain damage that results from a lack of oxygen and blood flow to the brain, or it can be secondary to other medical or neurological conditions.
- Cortical reflex myoclonus originates in the cerebral cortex (the outer layer of the brain that is largely responsible for information processing). Myoclonic jerks usually involve only a few muscles in one part of the body, but jerks involving many muscles also may occur. It becomes more intense when a person attempts to move in a certain way (action myoclonus) or perceives a particular sensation.
- Epileptic myoclonus is the presence of myoclonus in people living with epilepsy. Myoclonus can occur as the only seizure manifestation, as one component of a seizure, or one of multiple types of seizures 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, as well as generalized tonic-clonic seizures (affecting the whole body).
- Myoclonic-astatic epilepsy has generalized myoclonic jerks or seizures followed by a loss of muscle tone.
- Lennox-Gastaut Syndrome occurs 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 characterized by 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 is characterized by myoclonic seizures, progressive loss of memory, and impaired intellectual functions.
Who is more likely to get myoclonus?
Myoclonus may be caused by the following:
- A disturbance of the brain or spinal cord (the central nervous system, or CNS)—most common
- An injury to the peripheral nerves (the nerves outside the CNS that connect to sensory organs and muscles, and relay information from/to the CNS)—least common
Myoclonus can occur by itself or as one of several symptoms associated with a wide variety of nervous system disorders. For example, myoclonic jerks may develop in individuals with multiple sclerosis or epilepsy, and with neurodegenerative diseases such as Parkinson’s disease, Alzheimer’s disease, or Creutzfeldt-Jakob disease.
Myoclonus may also be seen in conjunction with infection, head or spinal cord injury, stroke, brain tumors, kidney or liver failure, chemical or drug intoxication, or metabolic disorders. Prolonged oxygen deprivation to the brain (hypoxia) may lead to post-hypoxic myoclonus.
Myoclonus can begin in childhood or adulthood with symptoms ranging from mild to severe.
Myoclonic twitches or jerks are caused by:
- Sudden muscle contractions (tightening), called positive myoclonus
- Muscle relaxation, called negative myoclonus
Studies suggest that the following locations in the brain are involved in myoclonus:
- Cerebral cortex, the most common origin for myoclonus
- Brain stem, close to structures that are responsible for the startle response, which is an automatic reaction to an unexpected stimulus involving rapid muscle contraction
However, the specific mechanisms underlying myoclonus are not yet fully understood. Scientists believe that 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 bring about myoclonus with the end result being a lack of inhibition at some level (inhibition is a decrease in the rate of a chemical reaction or its prevention).
Neurotransmitters carry messages between nerve cells. They are released by one nerve cell and attach to a protein called a receptor on neighboring (receiving) cells. Abnormalities or deficiencies in receptors for certain neurotransmitters may contribute to some forms of myoclonus, including receptors for:
- Serotonin, which is involved in managing mood, cognition, reward, learning, memory, physiological processes, etc.
- Gamma-aminobutyric acid (GABA), which is involved in motor control
- Glycine, which is important for the control of motor and sensory functions in the spinal cord
- Opioids, which are involved in different functions related to analgesia, pain, and depression
More research is needed to determine how these receptor abnormalities cause or contribute to myoclonus.
How is myoclonus diagnosed and treated?
Following a review of your medical history and physical exam, a doctor may order additional tests to confirm a diagnosis of myoclonus:
- Electromyography (EMG) to measure electrical activity of muscle
- Electroencephalography (EEG) to record the electrical activity of the brain that may trigger the myoclonic jerk through electrodes attached to the scalp
- Evoked potential studies to capture the electrical activity in the brain, brain stem, and spinal cord evoked by specific stimuli (tactile, auditory, visual stimulation)
- Laboratory urine or blood tests to look at possible causes and to rule out other conditions that may cause symptoms similar to myoclonus
- Magnetic resonance imaging (MRI) to produce three-dimensional images of the brain, spinal cord, nerve, and other tissue (including muscles).
A doctor’s first consideration in treating myoclonus is reversing or treating any underlying cause or the origin of the myoclonus. However, many cases require symptomatic treatment if the myoclonus is disabling.
Several options are available to help treat myoclonus:
- Clonazepam, a type of tranquilizer, is the most commonly used medication to treat some forms of myoclonus.
- Other drugs such as certain barbiturates, phenytoin, levetiracetam, valproate, and primidone are used to treat epilepsy in addition to myoclonus.
- Multiple medications may be required for effective treatment because some medications have a limited effect when used individually but may have a greater effect when combined with others.
- Hormonal therapy may improve responses to antimyoclonic drugs in some people.
- 5-hydroxytryptophan (5-HTP), a building block of serotonin (a chemical made in the body that transmits nerve impulses), leads to improvement in individuals with some types of action myoclonus and progressive myoclonus epilepsy. However, the effectiveness of 5-HTP therapy varies between individuals, and can make the condition worse in some individuals.
- Botulinum toxin injections can reduce excess muscle activity by blocking the activity of a chemical that makes muscles contract at the cellular level. It is the first-line therapy for hemifacial spasm (frequent spasms of the muscles on one side of the face) and has been effective in treating some individuals with palatal myoclonus.
What are the latest updates on myoclonus?
The National Institute of Neurological Disorders and Stroke ( NINDS ), a component of the National Institutes of Health (NIH), supports research on myoclonus at its laboratories in Bethesda, Maryland and through grants to major research institutions across the country. These research projects include:
- Biomarkers are measurable indicators of some biological state or condition and are often necessary for predicting the nature 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 children and adolescents between 12 to 20 years of age who are living with JME. Results may lead to novel clinical tools for diagnosis and personalized management.
- Glycogen is a form of sugar that is used as an energy reserve in many cells. Lafora bodies (LBs) are unusual, glycogen-like inclusions found in cells of all tissues in individuals suffering from Lafora body disease (or Lafora progressive myoclonus epilepsy). In another study, NINDS-funded researchers generate proteins that will help to degrade or break down LBs, which could lead to a novel therapeutic strategy to treat Lafora body disease.
- Researchers of the Lafora Epilepsy Cure Initiative determined the satisfactory performance of therapeutic agents against Lafora body disease and myoclonus epilepsy in pre-clinical trials with mice. A current NINDS-funded study will develop an Early Diagnosis Campaign to prepare a clinical trial ready group of people with early-stage and moderately advanced Lafora body disease and to identify clinical biomarkers of disease progression before advancing from mice therapeutics to human clinical trials.
- Botulinum toxin is a treatment for a variety of movement disorders. A NINDS study compared the use of ultrasound (using sound waves) and electrophysiologic guidance (using electrical stimulation and a needle) to precisely target muscles for botulinum toxin injection to treat upper limb spasticity and focal hand dystonia. Results may lead to improved treatment for movement disorders like myoclonus.
- Animal models are used to study the mechanisms involved in myoclonus. For example, NINDS-funded scientists have developed a mouse model of myoclonus-dystonia (an inherited movement disorder characterized predominantly by myoclonus of the upper body and dystonia). A striking characteristic of this disorder is that motor symptoms improve with alcohol consumption. Researchers tested the hypothesis that abnormal activity of the cerebellum (the part of the brain responsible for coordination and regulation of voluntary movement) causes myoclonus and dystonia in myoclonus-dystonia, and that by acting on targets in the cerebellum, alcohol injections normalize cerebellar activity to relieve motor symptoms. Results may provide a better understanding of the underlying neurological cause of myoclonus and dystonia in myoclonus-dystonia and provide targets for treatment options.
- Complex movement disorders (CMDs), or disorders in which individuals are affected by more than one movement disorder, such as parkinsonism and dystonia, or myoclonus and tremor, are a continuing challenge for diagnosis and treatment. NINDS-funded researchers are recruiting individuals with familial and sporadic CMDs to identify genetic mutations that may cause these disorders. Findings may lead to improvements in disease diagnosis and treatment.
In addition to NINDS , other NIH institutes and centers support research on movement disorders that include myoclonus. More information is available through the NIH RePORTER , a searchable database of current and previously funded research, as well as research results and publications.
For research articles and summaries on myoclonus, search PubMed , which contains citations from medical journals and other sites.
Learn About Clinical Trials
Clinical trials are studies that allow us to learn more about disorders and improve care. They can help connect patients with new and upcoming treatment options.
How can I or my loved one help improve care for people with myoclonus?
Consider participating in a clinical trial so clinicians and scientists can learn more about myoclonus. Clinical research uses human volunteers to help researchers learn more about a disorder and perhaps find better ways to safely detect, treat, or prevent disease.
All types of volunteers 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 Clinicaltrals.gov , a searchable database of current and past federal and private clinical studies.
Where can I find more information about myoclonus?
Learn about related topics
- Alzheimer’s Disease
- Brain and Spinal Cord Tumors
- Creutzfeldt-Jakob Disease
- Epilepsy and Seizures
- Multiple Sclerosis
- Parkinson’s Disease
- Spinal Cord Injury
- Traumatic Brain Injury
Myoclonus (Muscle Twitch)
Myoclonus is an uncontrollable muscle movement that’s sudden and brief. This can happen for a wide range of reasons. Many causes are normal and harmless, but myoclonus can also be a symptom of serious nervous system conditions. Depending on how and why it happens, this symptom may be treatable, and some conditions that cause it may be preventable.
What is myoclonus?
Myoclonus is a brief, sudden muscle movement (like a twitch, jerk or spasm). It happens when muscles incorrectly activate and usually lasts just a fraction of a second. It can affect a single muscle or a group of them. Some causes are more likely to affect muscles in your hands or feet, shoulders or hips, back or face.
Myoclonus (pronounced “my-OCK-lon-us”) can happen in people who are healthy at some point in their life. However, it’s also a possible symptom of several medical conditions, some of which are serious.
There are two main ways myoclonus happens:
- Positive myoclonus: This is when muscles contract or flex suddenly.
- Negative myoclonus: This is when muscles relax suddenly (the technical term for this is “asterixis,” and experts often describe it as a “hand-flapping tremor”).
What are the most common causes of myoclonus?
Myoclonus can happen for many reasons. Some of those reasons are normal and expected. Others happen because of specific conditions and disorders that affect various systems in your body. Experts divide myoclonus into four main categories.
Normal forms of myoclonus
Several processes in your body can cause myoclonus to happen for normal reasons. Experts call these examples of “physiological myoclonus.” They include:
- Hiccups (which are normal unless they last a couple of days or more).
- Sleep myoclonus (also known as hypnic jerks, these are sudden sharp muscle movements that happen as you fall asleep or wake up).
- Startle reflexes (a jump-like movement you can’t control when you’re surprised or scared).
Myoclonus can happen with or because of seizures (especially myoclonic seizures). This includes seizures due to different forms of epilepsy, such as Lennox-Gastaut syndrome or juvenile myoclonic epilepsy.
When myoclonus is a symptom of another condition, experts call this “secondary myoclonus.” Secondary myoclonus can happen for a wide range of reasons. Some of these only affect your brain or other areas of your nervous system. Others can affect many systems throughout your body.
Causes of secondary myoclonus include:
- Autoimmune diseases: These are conditions where your immune system mistakenly attacks your own body, such as celiac disease.
- Blood and body chemistry imbalances: These can happen with kidney or liver diseases and conditions affecting your thyroid. It can also happen because of vitamin or mineral deficiencies and electrolyte imbalances.
- Brain lesions: These are damaged areas of brain tissue. The damage disrupts how these areas work, which in turn causes myoclonus. Examples include damage from lack of oxygen (cerebral hypoxia) or lack of blood flow from a stroke.
- Degenerative brain diseases: Examples of these include Alzheimer’s disease and Lewy body dementia. It can also happen with Parkinson’s disease-related dementia.
- Genetic disorders: These conditions happen because of DNA mutations, including mutations you can inherit from your biological parents. Examples include Krabbe disease and Wilson disease.
- Infections: These often involve viral or bacterial infections that attack your brain or other parts of your nervous system, such as herpes simplex virus or Lyme disease.
- Nerve and spinal cord injuries: Damage to your spinal cord or nerves can interrupt your brain’s normal communication with parts of your body. Without that communication, those body parts may act spontaneously, causing myoclonus.
- Non-medical drugs and substances: Examples include alcohol, amphetamines, cocaine, ecstasy, heroin and more. Inhalants like toluene and gasoline can also cause myoclonus.
- Prescribed medications: Over a dozen different types of medication can cause myoclonus. These include anti-seizure medications, antidepressants, blood pressure medications, antibiotics, opioid painkillers and anesthetics.
- Poisons and toxins: Poisoning from heavy metals, such as lead, manganese and mercury, can cause myoclonus. It can also happen with other toxins, such as insecticides like methyl bromide.
Essential myoclonus is a condition that runs in families. This genetic form of myoclonus isn’t harmful and usually doesn’t get worse over time. But muscle movements may become more noticeable after drinking alcohol.
Care and Treatment
How is myoclonus treated?
Normal forms of myoclonus typically don’t need treatment. The treatment for other forms of myoclonus can vary widely. The treatments usually depend on the underlying cause, your medical history and more. Because the treatments can vary, a healthcare provider is the best person to tell you about the treatment options and which they recommend.
How can this symptom be prevented?
Myoclonus happens very quickly and often without warning. The normal and essential forms of it aren’t preventable.
However, some of the causes of secondary myoclonus are preventable. You may also be able to reduce how often epileptic myoclonus happens or how severe it is. Some things you can do include:
- Avoid non-medical drug use. This means avoiding the use of non-prescription drugs and using prescribed drugs in any way other than how your provider prescribed them. Tell your healthcare provider if you notice myoclonus after starting a new medication or non-medical drug use. Their job is to help you, not judge you, and they need to know about anything and everything you’ve taken so they can treat you safely and effectively.
- Protect your nervous system. Protective gear, such as helmets and safety belts, can help you prevent injuries to your brain, spinal cord and other parts of your nervous system.
- Manage chronic conditions. Epilepsy, thyroid disorders and other chronic conditions can cause myoclonus. Managing these conditions, as recommended by your provider, can help prevent myoclonus or reduce how often it happens.
When to Call the Doctor
When should this symptom be treated by a doctor or healthcare provider?
Normal forms of myoclonus don’t need treatment. If myoclonus keeps happening — especially if it starts disrupting your usual activities and routine — you should see a healthcare provider. Myoclonus that disrupts your life may be a sign of more serious issues.
Frequently Asked Questions
What are some other forms of myoclonus?
There are many forms of myoclonus, but some happen only in certain age groups or in very specific ways, including:
- Benign neonatal sleep myoclonus.
- Middle ear myoclonus.
- Opsoclonus myoclonus.
- Palatal myoclonus.
Benign neonatal sleep myoclonus (BNSM)
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.
Diagnosing this condition requires an electroencephalogram (EEG). This condition can look similar to seizures, but EEG testing in babies with BNSM won’t show seizure activity in their brains. This condition is harmless. About 95% of cases go away by 6 months of age.
Middle ear myoclonus
Middle ear myoclonus is when you have uncontrolled muscle movements of the tensor tympani, a muscle in your ear. Ordinarily, the tensor tympani tightens to protect your inner ear (like placing your hand on the top of a drum to dampen the sound). This usually happens when you talk, eat, cough, laugh or make other sounds through your mouth.
Middle ear myoclonus means the tensor tympani flexes at the wrong times. That can cause repetitive clicking, cracking or thumping sounds. It’s disruptive, but it isn’t dangerous. It’s often treatable with surgery or other methods.
Opsoclonus is similar to myoclonus, but it involves uncontrollable movements of the muscles that direct where you point your eyes. Opsoclonus-myoclonus syndrome (OMS) is a rare condition that involves both symptoms happening at the same time.
OMS sometimes happens because your immune system incorrectly attacks your own nervous system. In children, this faulty immune reaction may happen because of a type of brain cancer called neuroblastoma. In adults, it can happen with lung cancer, breast cancer or ovarian cancer. Other cases may have a connection to metabolic disturbances or infections. In many cases, healthcare providers aren’t able to identify a cause
Palatal myoclonus (also known as palatal tremor) is a form of myoclonus that affects a specific area inside your mouth. The soft palate is at the upper back of your mouth. It includes the uvula (the dangling teardrop-shaped piece of tissue) and surrounding soft tissue.
Myoclonus here can cause you to hear an unusual clicking sound. It can be inherited (essential palatal myoclonus) or as a symptom of a lesion in your brain. It can be disruptive. It’s often possible to treat it with medication.
A note from Cleveland Clinic
Myoclonus is a brief, sudden muscle movement (like a twitch or spasm). If you notice muscle jerks that are new and/or getting more frequent, you should talk to a healthcare provider. They’re the best person to help you discover why you’re experiencing this and what you can do about it. Many causes of myoclonus are treatable, and early diagnosis and treatment can make a big difference in keeping this condition’s effects on your life to a minimum.