What Is Involuntary Muscle Twitching (Myoclonus)?

If you have multiple sclerosis (MS), you may sometimes get muscle spasms, also called myoclonus. This is sudden jerking, quivering, or twitching of a muscle or group of muscles. You can have one episode or many in a row. And they can last as long as a few minutes.

Some types of myoclonus happen to healthy people. A hiccup or doing a double take when something startles you are common examples. But some people have myoclonus because of a health problem like MS, dementia, or Parkinson's disease.

Are There Different Types?

The types of myoclonus include:

Action myoclonus: It’s triggered by movement. It can affect your arms, legs, face, and voice.

Brainstem myoclonus: A sudden noise or something you see might cause a grimace. Your elbows, knees, neck, and other parts of your body may flex.

Cortical reflex myoclonus: This is the most common type of myoclonus. People who have this are prone to sudden jerk-like movements in their upper limbs and face.

Palatal myoclonus: This is a tremor in the roof or soft palate of your mouth. Your face, tongue, diaphragm, and throat may be involved. These muscle twitches come fast. You could have as many as 150 a minute. Bursts of movement might happen while you sleep.

Reticular reflex myoclonus: Twitching or jerking throughout your whole body can happen with this kind of myoclonus. Triggers include movements or something you see or hear.

Sleep myoclonus: Your muscles spasm while you sleep. It mainly affects your lips, eyes, fingers, and toes. It’s rare, but it might wake you up.

Are There Symptoms?

Whatever form myoclonus takes, people who have it agree that the movement is:

  • Sudden
  • Brief
  • Involuntary
  • Shock-like
  • Varied in intensity and frequency
  • In one part of the body or all over the body
  • Sometimes severe enough to get in the way of eating, speaking, or walking

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What Causes It?

Myoclonus happens because your nervous system isn't working the way it should. Something makes your nerve cells misfire and send the wrong signal to your muscles.

Doctors think several parts of your brain may be involved. But they aren't sure what causes this glitch in your nervous system. Sometimes, it just happens.

If you have MS, it could result from lesions, or injuries, on your brain or spinal cord.

Other nervous system conditions that can cause myoclonus include:

Sometimes the cause is a medical condition, such as:

How Is It Diagnosed?

Your doctor will do an exam and take note of which parts of your body have spasms. He may recommend the following:

Electroencephalogram (EEG): This tracks and records the patterns of electrical activity in your brain to figure out where the myoclonus starts. The doctor will put small discs (called electrodes) on your scalp. He’ll connect them to wires that send signals to a computer.

Electromyography (EMG): This test checks the health of your muscles and the nerve cells that control them. It uses electrodes to sense and record the signals your nerves send to your muscles.

Magnetic resonance imaging (MRI): Your doctor will use this test to take detailed pictures of your brain, spinal cord, and other body parts that might be involved.

He may also check your blood for signs of other causes, such as:

How Is It Treated?

Myoclonus can be hard to treat. Depending on your symptoms, you may have to take several medicines at the same time. That’s because they act on various parts of your brain. Drugs that can help myoclonus include:

Tranquilizers: Clonazepam (Klonopin) is often the first drug doctors use. It relaxes your muscles to keep them from twitching. Common side effects include feeling sleepy and being a bit clumsy. Because of that, your doctor will likely start with a very small dose. She'll prescribe bigger doses until your symptoms go away.

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Anti-seizure drugs: Medicines like levetiracetam (Keppra) and primidone (Mysoline) prevent seizures in people with epilepsy. But they can also help with myoclonus. Side effects include nausea, fatigue, and feeling dizzy.

Botox injections: The botulinum toxin "freezes" your muscles and keeps them from twitching. This may work best if myoclonus affects only one area of your body.

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Surgery: You might need it to remove the brain or spinal cord lesion that's causing your symptoms.

Deep brain stimulation (DBS): In this surgical procedure, your doctor implants electrodes into your brain and uses wire to connect them with a gadget implanted in your chest. You can use it to send out signals that block the ones causing your myoclonus. DBS can lower the number of muscle twitches, but like all surgeries, there are risks. Doctors are researching its use for MS. Right now, it’s mostly used a treatment for Parkinson’s disease.

WebMD Medical Reference Reviewed by Neil Lava, MD on March 10, 2018

Sources

SOURCES:

Mayo Clinic: “Myoclonus: Diagnosis & treatment,” “Myoclonus: Symptoms & causes.”

Cleveland Clinic: “Deep Brain Stimulation: Overview.”

National Institute of Neurological Disorders and Stroke: "Myoclonus Fact Sheet."

Baylor College of Medicine: "Myoclonus."

American Sleep Association: "Sleep Myoclonus."

Neurotherapeutics: "Treatment of Myoclonus."

UpToDate: "Treatment of myoclonus."

BMC Neurology: "Spinal segmental myoclonus in multiple sclerosis."

Therapeutic Advances in Neurological Disorders: "Myoclonic disorders: a practical approach for diagnosis and treatment."

National Organization for Rare Disorders: "General Myoclonus."

Journal of Neurology, Neurosurgery & Psychiatry: "Propriospinal myoclonus in multiple sclerosis."

Mayo Clinic: "Myoclonus."

Cleveland Clinic: "Deep Brain Stimulation: Overview."

Multiple Sclerosis Discovery Forum: "Deep Brain Stimulation Helpful in Some Patients with MS Tremor."

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