Myoclonic seizures

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Read about causes and symptoms of myoclonic seizures and how they are treated.

Key points

  • Myoclonic seizures can be generalized or partial and are a feature of many different epilepsy syndromes.
  • Symptoms include brief muscle jerks in the whole body or just in an arm or leg.
  • There is no specific intervention to protect your child or shorten the seizure.
  • Speak to your child's doctor about which medication is right to tackle your child's myoclonic seizure and its cause.

A myoclonic seizure is a sudden, brief, shock-like muscle contraction. It can be a generalized or partial seizure and appears most often during the first year of life.

What are other terms for myoclonic seizures?

Other terms for myoclonic seizures include:

  • myoclonus
  • myoclonic jerk.

How can you tell if your child has myoclonic seizures?

Myoclonic seizures

A child having a myoclonic seizure will have one or many brief muscle jerks, either in the whole body or just in one arm or leg. Unlike clonic seizures, the jerks are not rhythmic. Sometimes myoclonic seizures are not strong enough to cause visible movement, but the child feels a shock-like feeling in their muscles.

In some syndromes, such as juvenile myoclonic epilepsy, myoclonic seizures happen in the morning just after the child wakes up. Objects such as toothbrushes or mugs may fly out of the child’s hands. The child and their parents may assume that they are just sleepy or clumsy.

How many other children have myoclonic seizures?

Up to 10 percent of children with epilepsy have myoclonic seizures.

What causes myoclonic seizures?

Myoclonic seizures are seen in many different epilepsy syndromes, including benign myoclonic epilepsy of infancy, juvenile absence epilepsy, juvenile myoclonic epilepsy, Lennox-Gastaut syndrome, and the progressive myoclonus epilepsies. For this reason, it is often difficult for a doctor to tell exactly what syndrome a child has. To make the diagnosis, the doctor will look at the location of the seizures, their symmetry, the child’s EEG pattern and any factors that trigger the seizures.

How are myoclonic seizures treated?

Anti-epileptic drugs are used to treat myoclonic seizures. Which one is chosen usually depends on the specific epilepsy syndrome. Vagus nerve stimulation (VNS) treatment or the ketogenic diet may also be used.

What should I do when my child has a myoclonic seizure?

There is no specific intervention for a myoclonic seizure. If seizures occur in prolonged clusters, your doctor may prescribe a medication to help stop the clusters. Continuous myoclonic seizures may require urgent treatment.

What is the outlook for a child with myoclonic seizures?

The outlook depends largely on the diagnosis. Some epilepsy syndromes will go away when the child gets older. In some cases, the child may need to keep taking anti-epileptic drugs all their life but will otherwise develop normally. A few syndromes that cause myoclonic seizures also cause neurological deterioration, which can have serious consequences.​

Last updated: February 4th 2010