What are they like?

Here's a typical story: "When Jeff has an episode, he just stiffens up. Both arms are raised over his head and his face has a grimace, as if someone is pulling on his cheeks. If he's standing, he may lose his balance and fall. These seizures don't knock him out like the tonic-clonic seizures, but if he has a few close together, he is often tired."

How long do they last?

Usually less than 20 seconds.

Tell me more

Muscle "tone" is the muscle's normal tension at rest. In a "tonic" seizure, the tone is greatly increased and the body, arms, or legs make sudden stiffening movements. Consciousness is usually preserved. Tonic seizures most often occur during sleep and usually involve all or most of the brain, affecting both sides of the body. If the person is standing when the seizure starts, he or she often will fall.

Who gets them?

They are particularly common in people who have the epilepsy syndrome called Lennox-Gastaut syndrome, but they can occur in anyone.

What's the outlook?

Tonic seizures in Lennox-Gastaut syndrome may become more difficult to control over time. Some patients do achieve a good outcome.

What else could it be?

Children with neurological impairments sometimes make movements that could be mistaken for tonic seizures. The EEG should be able to tell the difference.

How is the diagnosis made?

The EEG can clearly show these seizures if they occur during monitoring.

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