Myoclonus: Types, Causes and Treatment

Ever felt a sudden jerk or jump-like sensation just as you were drifting off to sleep? That brief, involuntary movement is called myoclonus. Most people experience it occasionally, especially while falling asleep and it is usually nothing to worry about. But myoclonus can also be linked to epilepsy, other neurological conditions, certain medicines, or metabolic problems.

Myoclonus is not a disease in itself. It is a way of describing a specific type of movement. That is why figuring out what is causing it is such an important part of diagnosis and treatment.

What is Myoclonus?

Myoclonus is a sudden, brief, involuntary jerking or twitching of a muscle or group of muscles. The movement usually lasts only a fraction of a second, although it can be felt repeatedly.

Most myoclonus results from a sudden muscle contraction, known as positive myoclonus. Less commonly, it occurs because an already going muscle contraction suddenly stops. This is called negative myoclonus.

For example, a person with negative myoclonus may briefly lose muscle control when holding a cup and drop it.

The movement can be experienced at rest, during an action, while maintaining a posture or in response to a stimulus such as a sudden sound or touch. When and how it happens can offer doctors important hints about what is causing it.

Symptoms of Myoclonus

The main symptom is a sudden, brief muscle jerk that a person cannot voluntarily control.

Depending on its type and severity, myoclonus may cause:

• Sudden jerking or twitching of the arms, legs, face or trunk
• Repeated movements in a short period
• Jerks triggered by movement, touch, sound or surprise
• Difficulty holding objects
• Problems with walking or coordination
• Difficulty eating or speaking when muscles involved in these activities are affected
• Jerking movements during sleep or while falling asleep

Some people experience an isolated jerk from time to time, whereas others may have frequent movements that interfere with everyday activities.

What are the Types of Myoclonus?

Neurologists may classify myoclonus according to why it occurs, where it starts in the nervous system or when it happens.

Physiological myoclonus

This is common in otherwise healthy people and usually does not need any treatment. For example:

• Sudden jerks while falling asleep
• Hiccups
• Normal startle responses
• Some muscle jerks associated with exercise or anxiety

So, not every muscle jerk means there is an underlying neurological disorder.

Essential myoclonus

Here, myoclonus occurs on its own without another identifiable neurological disorder causing it. It is usually stable or progresses very slowly. Some forms may run in families.

Epileptic myoclonus

Myoclonic jerks can also be experienced as part of epilepsy, a neurological condition that causes seizures. One example is juvenile myoclonic epilepsy, which commonly begins around adolescence and may cause brief jerks involving the shoulders, arms or neck.

A myoclonic jerk does not confirm that a person has epilepsy. However, the pattern and, when appropriate, tests such as an EEG help neurologists determine whether the movements are seizure-related.

Secondary or symptomatic myoclonus

This type is usually experienced because of another condition or external factor. It can be associated with neurological diseases, metabolic problems, infections, brain injury, stroke, certain medicines and toxins.

What Causes Myoclonus?

Myoclonus results from abnormal electrical signalling in the nervous system’s movement pathways.

Some possible causes of myoclonus are:

• Epilepsy and seizure disorders
• Parkinson’s disease and other neurodegenerative disorders
• Stroke or traumatic brain or spinal cord injury
• Brain or spinal cord lesions
• Infections or inflammation affecting the nervous system
• Kidney or liver failure
• Abnormal blood glucose or electrolyte levels
• Certain genetic disorders
• Autoimmune conditions
• Exposure to certain drugs or toxins
• Some prescription medicines

A medication review is particularly useful because some medicines can cause myoclonus. If jerking begins after starting or changing a medicine, tell your doctor.

How is Myoclonus Diagnosed?

Diagnosis begins with a detailed medical history and neurological examination. The neurologist may ask:

• when the jerks began
• how often they occur
• whether they happen during sleep or movement
• whether anything triggers them

The evaluation may include:

• Blood and urine tests to look for metabolic problems, infection or exposure to drugs or toxins
• EEG (electroencephalogram) to record electrical activity in the brain and determine whether jerks are associated with seizures
• EMG (electromyography) to measure electrical activity in muscles
• MRI to look for structural abnormalities in the brain or spinal cord
• Genetic testing when an inherited condition is suspected

The investigations are selected according to the movement pattern and suspected underlying cause.

How is Myoclonus Treated?

Treatment depends largely on what is causing the myoclonus. When an underlying condition, medicine or metabolic problem can be identified, addressing that cause is usually the first step.

1. Medication

Neurologists or movement disorder specialists may prescribe medicines that reduce abnormal nervous system activity.

2. Botulinum toxin (BOTOX)

For selected focal or segmental forms, botulinum toxin injections (BOTOX) can reduce excessive activity in specific muscles. This approach is particularly useful when jerking is limited to a small, well-defined group of muscles.

3. Treating the underlying condition

If myoclonus results from an electrolyte imbalance, kidney or liver problem, infection, medication or another neurological condition, treating that problem may reduce the jerking.

In some complex cases, other approaches such as immunotherapy, surgery or deep brain stimulation (DBS) may be considered depending on the underlying diagnosis.

Is Myoclonus Serious?

• Not always. Sleep starts and hiccups are common physiological forms of myoclonus and are generally harmless.
• However, frequent jerks deserve medical attention when they interfere with your everyday activities, are progressively worsening, or occur alongside other neurological symptoms.
• One useful observation for patients is to note when the jerks happen. Do they occur while falling asleep, during movement, after a sudden sound, or while sitting still? Sharing these details with a specialist can make the diagnostic process more informative.

When Should You See a Doctor?

You should consider consulting a neurologist if:

• Jerking movements are frequent or persistent
• They interfere with eating, walking, speaking or other daily activities
• The movements are becoming more severe
• They begin after starting a new medicine
• They occur with loss of awareness or other possible seizure symptoms
• They are accompanied by weakness, changes in coordination or other neurological symptoms

A movement disorder specialist or neurologist can determine whether the movements represent myoclonus and investigate the underlying cause.

Conclusion

If sudden jerking movements are becoming frequent or affecting your daily life, an evaluation with a specialist can help identify whether they are harmless or related to an underlying condition. The Neurology and Neurosciences Department at the CK Birla Hospital can help evaluate movement disorders such as myoclonus and determine an appropriate diagnostic and treatment approach. Simply book a consultation to get expert guidance.