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.
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:
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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.
Several processes in your body can cause myoclonus to happen for normal reasons. Experts call these examples of “physiological myoclonus.” They include:
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:
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.
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.
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:
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.
There are many forms of myoclonus, but some happen only in certain age groups or in very specific ways, including:
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 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.
Last reviewed by a Cleveland Clinic medical professional on 03/16/2023.
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