What is myoclonus?

Myoclonus is a brief, uncontrollable twitching of the muscles, also known as myoclonic jerks. It can be alarming to experience, however it’s generally treatable with medication or surgery.

Myoclonus can be mild or severe and may occur in virtually any muscle group. It’s usually a symptom of a broader health issue and can be caused by multiple factors, including disruptions in the brain, spinal cord, or central nervous system. It may also be caused by peripheral nerve injury, though this is less common.

Penn Medicine provides expert treatment of myoclonus and its associated conditions. Our specialists focus on providing relief for the symptom itself while diagnosing its root cause. 

Symptoms of myoclonus

Myoclonic jerks can begin either as isolated incidents or as part of a pattern. They can happen once or multiple times in a short period or in direct response to outside factors.

Though generally grouped into two main categories, there are also many subcategories of myoclonus that determine its impact on overall health and quality of life. The main categories of myoclonus include:

  • Physiologic myoclonus: This is the less concerning form of myoclonus and includes symptoms like hiccups or twitching in the arms or legs before and during sleep. Physiologic myoclonus is characterized by singular, isolated periods of muscle twitching that cease on their own and cause no real damage.
  • Pathologic myoclonus: This type of myoclonus is often symptomatic of a broader issue related to the brain or central nervous system. It can include sudden, often sharp, and painful contractions of the muscles that start in one area and spread throughout the body. Pathologic myoclonus can also occur in reaction to certain types of medication. In more severe cases, it can impact mobility, speech, and the ability to eat.

Within these two categories, more specific types of myoclonus can include:

  • Sleep myoclonus
  • Essential myoclonus
  • Stimulus-sensitive myoclonus
  • Action myoclonus
  • Cortical reflex myoclonus
  • Epileptic myoclonus (seizures)
  • Reticular reflex myoclonus
  • Palatal myoclonus (also known as palatal tremor)
  • Spinal myoclonus
  • Peripheral myoclonus

Myoclonus causes

Myoclonic jerks and twitches are usually caused by sudden tightening and relaxation of the muscles. This twitching can be related to many conditions ranging from mild to severe, including:

  • Infection
  • Brain or spinal cord injury
  • Brain tumor
  • Stroke
  • Organ failure
  • Metabolic disorders
  • Ischemic disorder
  • Substance use and intoxication
  • Lack of oxygen to the brain (hypoxia)

These conditions are often identified through the presence of myoclonus and many other symptoms, so it's important to seek proper testing to determine their origins. Myoclonic seizures are often caused by different types of epilepsy affecting various age groups.

While there's evidence to suggest that myoclonus can start in the cerebral cortex and brain stem, it's not yet definitively known what neurobiological factors cause these episodes. Other research suggests that certain types of myoclonus may be the result of an imbalance or misfiring of neurotransmitters that relay messages between nerve cells.

How is myoclonus diagnosed?

Diagnosing myoclonus usually starts with a complete physical exam and a comprehensive assessment of your medical history. After these steps, your doctor may recommend additional testing for a definitive diagnosis. These tests may include:

  • Electromyography (EMG), which measures muscle groups' electrical activity
  • Electroencephalography (EEG), in which electrodes are attached to the scalp to measure electrical activity in the brain
  • Urine or blood tests to identify or rule out possible underlying conditions
  • Magnetic resonance imaging (MRI) to view images of the brain, spinal cord, nerve tissue, and different muscle groups

Other tests for myoclonus may include a lumbar puncture to examine spinal fluid and tests to measure electrical activity in the brain or spinal cord in response to external factors.

When should I seek treatment for myoclonus?

You’ll want to seek treatment for myoclonic jerking if it’s severe and persistent or interferes with your quality of life. If myoclonus occurs frequently, and is a noticeable concern, it may mean there’s a more serious underlying health issue that requires diagnosis and care. Your doctor may examine your myoclonic episodes with other symptoms to form a treatment plan.

If your myoclonus is severe to the point of seizures, your care team may take more immediate action to treat the symptom while forming a parallel care plan for any possible underlying condition.

Expert myoclonus care at Penn Medicine

Penn Medicine offers the latest advancements in diagnostic techniques and medical and surgical treatment for those with epilepsy and seizure disorders. Our team at Penn's Comprehensive Epilepsy Center is recognized as a national leader in epilepsy treatment and seizure management—even for rare and complex cases.

We also offer diagnosis and treatment for other conditions that may cause myoclonus, including movement disorders, stroke, and sleep conditions. In addition to prioritizing treatment of the underlying condition that's causing your myoclonus, Penn Medicine's neurology specialists will provide symptomatic care if your myoclonus is severely impacting your quality of life with the aim to make you as comfortable and pain-free as possible.

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