What to Know About Myoclonic Seizure

Medically Reviewed By Nancy Hammond, M.D.
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A myoclonic seizure is a neurological disorder that causes a sudden spasm or jerking in your muscles. These mild seizures can happen in several types of epilepsy and are easily mistaken for nervousness or a tic. A myoclonic seizure usually lasts for less than a second. However, they can come in clusters.

This article explains the causes and triggers of myoclonic seizures before detailing their signs and symptoms, treatment options, and more.

What are the causes and triggers of myoclonic seizures?

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If you have an epileptic disorder, neurons in your brain may sometimes signal unusually. This unusual signaling can cause sudden and involuntary muscle contractions called seizures. A myoclonic seizure is a generalized seizure, meaning that irregular neuronal activity happens on both sides of the brain.

In up to 50% of people with epilepsy, there is no identifiable cause. However, any factor that disturbs typical neural activity in the brain can lead to seizures. Common causes include:

Learn nine things doctors want you to know about epilepsy here.

What are the signs and symptoms of myoclonic seizures?

The word “myoclonic” describes what you will see in a myoclonic seizure: “myo” meaning muscle and “clonus” meaning rapidly alternating contractions and relaxations. A myoclonic seizure is a sudden, very short, non-rhythmic jerking movement that lacks a discernible pattern. Myoclonic seizures can happen on their own or in clusters.

Myoclonic seizures cause jerks or twitches of the upper body, arms, or legs. You will most likely recover immediately after a seizure and simply continue doing whatever you were doing before the seizure.

If myoclonic seizures happen when you are standing, they may cause you to fall.

When should I seek medical attention for myoclonic seizures?

A single myoclonic seizure does not require any kind of first aid. If the seizures are repetitive and last for several minutes, however, call for immediate help. If this happens, the seizures may be a symptom of a more serious disorder. 

When to seek emergency medical attention for myoclonic seizures

Dial 911 or seek immediate medical attention in the following cases:

  • The seizure lasts for longer than a few seconds.
  • You have multiple seizures in a short time.
  • You become unconscious during a seizure.
  • You have difficulty breathing or waking up after the seizure.
  • You have a chronic condition.
  • You sustain an injury during the seizure.

First aid for someone else having myoclonic seizures

Take these steps to prevent injury:

  • Try to remain calm.
  • Remove any nearby objects that could cause harm.
  • Do not try to restrain the movements of the person having the seizure.

What types of epilepsy can cause myoclonic seizures?

Myoclonic seizures can appear in a variety of epilepsy syndromes, including those described below.

Juvenile myoclonic epilepsy

Juvenile myoclonic epilepsy (JME) is one of the most common childhood epilepsy syndromes.

One 2021 article on JME suggested that about 5–10% of children with epilepsy have JME. It is seen in both sexes equally, though some studies have reported a higher incidence in females. The same study suggested that JME usually manifests between 12 and 18 years of age. In about 50% of cases, it appears to be hereditary.

The seizures usually involve the neck, shoulders, and upper arms. In many children, the seizures most often occur soon after waking up.

People with JME can also have tonic-clonic seizures and absence seizures.

Learn about tonic-clonic seizures here.

Lennox-Gastaut syndrome

Lennox-Gastaut syndrome (LGS) is an uncommon, severe epilepsy syndrome. It usually includes other types of seizures as well. It begins in early childhood.

The myoclonic seizures usually involve the neck, shoulders, upper arms, and face. One 2021 analysis of available data suggested that LGS seizures are often resistant to antiseizure medications.

Symptoms include many types of seizures, severe learning disabilities, and serious physical limitations. LGS seizures are hard to treat and often resistant to drug therapies.

Progressive myoclonic epilepsy

Progressive myoclonic epilepsy includes several different syndromes. These syndromes typically include multiple types of seizures that are difficult to control, learning and developmental challenges, and physical impairments.

  • Progressive myoclonus 1: This is a rare genetic condition. Symptoms include severe myoclonic seizures, other seizures, balance problems, and learning difficulties.
  • Progressive myoclonus 2: This is a rare genetic metabolic disorder. Symptoms can include vision loss and severe learning disabilities.
  • Mitochondrial encephalomyopathy: These rare genetic conditions impair your ability to produce energy. Symptoms include low energy, muscle disease, and brain dysfunction.
  • Neuronal ceroid lipofuscinosis: This condition can lead to balance problems, learning deficits, vision loss, and multiple types of seizures.

Learn more about different types of epilepsy here.

How do doctors diagnose myoclonic seizures?

To make a diagnosis, your doctor will begin by taking your medical history and your family history. The National Institute of Neurological Disorders and Stroke lists the following tests that can help your doctor reach an accurate diagnosis.

Electroencephalogram tests

These track the brain’s electrical activity to detect anomalies. They should be done when you are awake as well as when you are drowsy. This is because brain activity during drowsiness or sleep more closely resembles brain activity during epilepsy.

Imaging tests

The most commonly used brain scans include CT, PET, and MRI scans. CT and MRI scans can show structural anomalies of the brain, including tumors and cysts.

A functional MRI scan can help localize normal brain activity and detect irregularities in functioning.

Single-photon emission CT scans can be used to locate seizure foci in the brain. A test called an ictal SPECT can help detect the area in the brain that is causing the seizures.

Blood tests

Blood tests can help screen for metabolic or genetic disorders that may be associated with the seizures. They can also help detect underlying health conditions — such as infections, lead poisoning, anemia, and diabetes — that may be causing or triggering the seizures.

Read our appointment guide for epilepsy here.

Myoclonic seizures vs. epilepsy

Epileptic disorders are caused by unusual electrical activity in the brain. The unusual signaling can cause sudden and involuntary muscle contractions called seizures.

Myoclonic seizures are one type of seizure that may appear in some types of epilepsy.

How do doctors treat myoclonic seizures?

Myoclonic seizures are manageable by treating the epileptic disorder that they are part of. The sections below outline this in more detail.

Juvenile myoclonic epilepsy

A 2017 paper suggested that JME can be effectively treated with antiepileptic drugs such as valproic acid. In two-thirds of participants, seizures stopped.

The same study indicated that myoclonic seizures may disappear or diminish in the fourth decade of life. Around 15–30% of participants were later able to discontinue their medication without their seizures coming back.

Lennox-Gastaut syndrome

A 2021 analysis suggested that freedom from seizures in LGS is rarely possible. Treatment, therefore, focuses on controlling the frequency and severity of the seizures by using a combination of antiseizure medications. At the same time, your doctor will help you find a treatment plan that encourages cognitive function and fosters neurodevelopment.

Progressive myoclonic epilepsy

Depending on your type of epilepsy, your doctor may recommend a treatment plan that includes the following drugs:

  • valproic acid
  • clonazepam
  • piracetam
  • phenobarbital
  • levetiracetam
  • piracetam
  • topiramate
  • zonisamide

Emergency treatment may include:

  • intravenous diazepam
  • lorazepam
  • clonazepam
  • midazolam
  • valproic acid
  • levetiracetam

Learn more about drugs for epilepsy here.

Summary

A myoclonic seizure is a mild seizure that causes a sudden spasm or jerking in your muscles. It appears in several types of epileptic disorders.

In many cases, myoclonic seizures can be controlled using antiseizure medications.

Usually, myoclonic seizures do not require medical treatment. However, contact a doctor if they are happening regularly or if you develop injuries because of them.

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Medical Reviewer: Nancy Hammond, M.D.
Last Review Date: 2022 May 31
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THIS TOOL DOES NOT PROVIDE MEDICAL ADVICE. It is intended for informational purposes only. It is not a substitute for professional medical advice, diagnosis or treatment. Never ignore professional medical advice in seeking treatment because of something you have read on the site. If you think you may have a medical emergency, immediately call your doctor or dial 911.