Myoclonic seizures

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?

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 they are holding at the time, 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.

My child has muscle jerks sometimes in sleep. Can these be normal?

Brief muscle jerks can happen in children and adults who do not have epilepsy, especially when going to sleep or during sleep. These are normal movements and do not suggest the presence of epilepsy. These should disappear when the child wakes up.

How common are myoclonic seizures?

Up to 10 per cent of children with epilepsy have myoclonic seizures.

What causes myoclonic seizures?

Myoclonic seizures are seen in many different epilepsy syndromes, including self-limited myoclonic epilepsy of infancy, juvenile absence epilepsy, juvenile myoclonic epilepsy, Lennox-Gastaut syndrome, and the progressive myoclonus epilepsies. To make the diagnosis, your child’s health-care team will review the history of other seizure types, presence of developmental delay or regression, family history, the child’s EEG pattern and any factors that trigger the seizures.

How are myoclonic seizures treated?

Anti-seizure medications 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 when medications are not effective.

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 child’s health-care provider 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?

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