What are they like?

Here's a typical story: "In the morning, I get these 'jumps.' My arms fly up for a second, and I often spill my coffee or drop what I'm holding. Now and then my mouth may shut for a split second. Sometimes I get a few jumps in a row. Once I've been up for a few hours, the jumps stop."

How long do they last?

They're very brief jerks. 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.

Tell me more

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.

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 things are normal.

In epilepsy, myoclonic seizures usually 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:

• Juvenile myoclonic epilepsy: The 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.
• Lennox-Gastaut syndrome: This 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 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.

Who gets them?

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.

What's the outlook?

The outlook for patients with the various syndromes that include myoclonic seizures varies widely. See the specific syndromes for more information.

What else could it be?

As mentioned, some episodes of myoclonus are normal. Some myoclonic seizures occur in reflex epilepsies, triggered by flashing lights or other things in the environment.

How is the diagnosis made?

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

Topic Editor: Orrin Devinsky, M.D.
Last Reviewed:2/11/04

source: http://www.epilepsy.com/epilepsy/seizure_myoclonic