Myoclonic Seizures

What Is A Myoclonic Seizure?

Myoclonic (MY-o-KLON-ik) seizures are brief, shock-like jerks of a muscle or a group of muscles. “Myo” means muscle and “clonus” (KLOH-nus) means jerking or twitching of a muscle. Usually, these seizures don’t last more than a second or two. There can be just one, but sometimes many will occur in series over a short time (>20 jerks in a row).

Even people without epilepsy can experience myoclonus in hiccups or in a sudden jerk that may wake you up as you’re just falling asleep. These events are normal.

In epilepsy, myoclonic seizures are seen on the EEG as an abnormal brain wave pattern. They often cause abnormal movements on both sides of the body at the same time. They occur in a variety of epilepsy syndromes that have different characteristics:

  • Lennox-Gastaut syndrome: Myoclonic seizures in LGS usually involve the neck, shoulders, upper arms, and often the face. They may be quite strong and are difficult to control.
  • Progressive myoclonic epilepsy: The rare syndromes in this category feature a combination of myoclonic seizures and tonic-clonic seizures. Treatment is usually not successful for very long, as the patient deteriorates over time. Those with progressive myoclonic epilepsy may also have LGS.

How Can I Tell If Someone Is Having A Myoclonic Seizure?

These seizures can be easily overlooked because they are so brief and appear as extra normal movements. These seizures can be mistaken for tics, tremors, or clumsiness.

Myoclonic Seizures in LGS

(WARNING! Graphic Content)


Thank you to the families who shared these heartbreaking videos with us so we may educate others. An EEG is the only way to determine the exact seizure type. We did not have EEG for these video’s so thank you to the physicians, who, as a part of their daily practice, regularly review videos of their patients having seizures and have reviewed these videos to help us best determine the seizure type represented.

First aid:

Roll the person on their side so they don’t breathe any saliva or other secretions into their lungs (aspirate). This can lead to pneumonia. Make sure the person is breathing is okay, and ensure they don’t injure themselves. Time the seizure.

Emergency Care:

A seizure that lasts more than 5 minutes (status epilepticus), or three seizures in a row without a clear recovery between them (seizure cluster), is a medical emergency. Administer at-home seizure rescue medication immediately and if the seizure does not resolve, call for emergency help.

The information here is not intended to provide diagnosis, treatment, or medical advice and should not be considered a substitute for advice from a healthcare professional. Content provided is for informational purposes only. LGSF is not responsible for actions taken based on the information included on this webpage. Please consult with a physician or other healthcare professional regarding any medical or health-related diagnosis or treatment options.

Click Here to Return to Seizure Types Associated with LGS

Updated February 26, 2022