Myoclonic Seizures

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 rapidly alternating contraction and relaxation—jerking or twitching—of a muscle. Usually, they don't last more than a second or two. There can be just one, but sometimes many will occur within a short time.

Sometimes myoclonus can occur in people without epilepsy. An example would be a sudden jerk that may wake you up as you're just falling asleep. 

The term “myoclonic seizure” is used if myoclonus results from abnormal brain activity. In epilepsy, myoclonic seizures usually cause quick jerking movements on both sides of the body at the same time. They occur in a variety of epilepsy syndromes that have different characteristics:

Juvenile Myoclonic Epilepsy

Juvenile myoclonic epilepsy (JME) seizures usually involve the neck, shoulders, and upper arms. In many patients the seizures most often occur soon after waking up. They usually begin around puberty or sometimes in early adulthood in people with a normal range of intelligence. In most cases, these seizures can be well controlled with medication, but it must be continued throughout life. Myoclonic seizures in juvenile myoclonic epilepsy may be triggered by being overtired or by flashing lights.

Lennox-Gastaut Syndrome

Lennox-Gastaut syndrome is an uncommon syndrome that usually includes other types of seizures as well. It begins in early childhood. The myoclonic seizures usually involve the neck, shoulders, upper arms, and often the face. They may be quite strong and are difficult to control.

Progressive Myoclonic Epilepsies

The rare syndromes in this category feature a combination of myoclonic seizures and tonic-clonic seizures. Treatment is usually not successful for very long for progressive myoclonic epilepsies (PME). Treatment is difficult as the patient deteriorates over time, and often develops other symptoms such as intellectual disability, coordination and walking problems.