What are they like?

Here's a typical story from a parent's view: "These seizures frighten me. They only last a minute or two but it seems like an eternity. I can often tell Heather's going to have one because she acts cranky and out of sorts. It begins with an unnatural shriek. Then she falls, and every muscle seems to be activated. Her teeth clench. She's pale, and later she turns slightly bluish. Shortly after she falls, her arms and upper body start to jerk, while her legs remain more or less stiff. This is the longest part of the seizure. Finally it stops and she falls into a deep sleep."

How long do they last?

Generally, 1 to 3 minutes. A tonic-clonic seizure that lasts longer than 5 minutes probably calls for medical help. A seizure that lasts more than 30 minutes, or three seizures without a normal period in between, indicates a dangerous condition called convulsive status epilepticus. This requires emergency treatment.

Tell me more

This type is what most people think of when they hear the word "seizure." An older term for them is "grand mal." As implied by the name, they combine the characteristics of tonic seizures and clonic seizures. The tonic phase comes first: All the muscles stiffen. Air being forced past the vocal cords causes a cry or groan. The person loses consciousness and falls to the floor. The tongue or cheek may be bitten, so bloody saliva may come from the mouth. The person may turn a bit blue in the face. After the tonic phase comes the clonic phase: The arms and usually the legs begin to jerk rapidly and rhythmically, bending and relaxing at the elbows, hips, and knees. After a few minutes, the jerking slows and stops. Bladder or bowel control sometimes is lost as the body relaxes. Consciousness returns slowly, and the person may be drowsy, confused, agitated, or depressed.

Who gets them?

They affect both children and adults.

What's the outlook?

For children who have had a single tonic-clonic seizure, the risk that they will have more seizures depends on many factors. Some children will outgrow their epilepsy. Often, tonic-clonic seizures can be controlled by seizure medicines. Many patients who are seizure-free for a year or two while taking seizure medicine will stay seizure-free if the medicine is gradually stopped. The risk that an individual will have more seizures depends on factors such as whether his or her EEG shows any epilepsy waves, or whether the doctor finds any abnormalities on a neurological exam. Among children with no epilepsy waves and a normal exam, about 70% of those who have had tonic-clonic seizures will stay seizure-free without medication. The comparable number is less than 30% for children with epilepsy waves and an abnormal exam. All these figures are more favorable than those for partial seizures.

What else could it be?

Some nonepileptic (psychogenic) seizures resemble tonic-clonic seizures. The surest way to tell the difference is with video-EEG monitoring. In some cases, the same person may have both tonic-clonic and nonepileptic seizures.

People who faint sometimes develop tonic or clonic movements. These movements are rarely as intense or prolonged as a tonic-clonic seizure.

How is the diagnosis made?

The typical appearance of a tonic-clonic seizure is usually easy to recognize. The doctor will want a detailed description of the seizures. An EEG and other tests may help to confirm the diagnosis or suggest a cause.

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