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.

The epileptic syndromes that most commonly include myoclonic seizures usually begin in childhood, but the seizures can occur at any age. Other characteristics depend on the specific syndrome.

With a myoclonic seizure, there is usually a brief jerk of the body. This may result in someone dropping an object, or less commonly can lead to a fall. 

When a myoclonic seizure ends, the person usually continues doing whatever they were doing before and during the seizure. They are awake and able to think clearly. No first aid is needed because of this seizure.

Myoclonic seizures can occur as single events or may cluster, with several occurring over a short time.

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.

The seizures themselves are easy to identify. The syndromes usually can be diagnosed on the basis of the medical history and often an EEG test.

There are several medicines that can help prevent myoclonic seizures. Myoclonic seizures often respond well to the appropriate medicine.

If you think that you or your loved one are having myoclonic seizures, talk to your child’s doctor or your own and share your concerns right away. Because myoclonic seizures are often associated with certain syndromes, seeing a doctor quickly to make a diagnosis and begin treatment is essential.

Authored By:

Joseph I. Sirven MD
Orrin Devinsky, MD

on Friday, July 19, 2013

Reviewed By:

Joseph I. Sirven MD
Patty Obsorne Shafer RN, MN

on Saturday, March 19, 2022


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