Myoclonus (Muscle Twitch)

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).

Epileptic myoclonus

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.

Secondary myoclonus

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

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.

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 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.

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-myoclonus syndrome

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

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.