• Clonic means repeated jerking.
  • Clonic seizure movements cannot be stopped by restraining the person.
  • Clonic seizures are rare.
  • Much more common are tonic-clonic seizures, involving jerking and stiffening of the muscles.

What is a clonic seizure?

"Clonus" (KLOH-nus) means rapidly alternating contraction and relaxation of a muscle -- in other words, repeated jerking. The movements cannot be stopped by restraining or repositioning the arms or legs. Clonic (KLON-ik) seizures are rare. Much more common are tonic-clonic seizures, in which the jerking is preceded by stiffening (the "tonic" part). Sometimes tonic-clonic seizures start with jerking alone. These are called clonic-tonic-clonic seizures! These seizures tend to last for a few seconds to a minute.

Brief and infrequent clonic seizures in infants usually disappear on their own within a short time. Other types may need prolonged treatment

Who is at risk for clonic seizures?

Clonic seizures are not seen very often. They can occur at various ages, including in newborns.

What’s it like to have a clonic seizure?

Clonic seizures consist of rhythmic jerking movements of the arms and legs, sometimes on both sides of the body.

What happens after a clonic seizure?

When a clonic seizure ends, the person may simply continue what they are doing. First aid is not a typical requirement for this seizure type.

If someone has clonic seizures, how often will they happen?

It depends a lot on the cause and the person. Some people may have rare seizures and others may have them more frequently.

How can I tell if someone is having a clonic seizure?

Clonic seizures consist of rhythmic jerking movements of the arms and legs, sometimes on both sides of the body.

Occasionally "jitteriness" in a young infant can be mistaken for a clonic seizure, especially if it is severe (during crying, for instance). Changing the position of the baby's arms or legs should reduce or stop jitteriness. The jittery infant also will be more alert than an infant who is having a clonic seizure.

Children with neurological impairments sometimes have repetitive movements that could be mistaken for clonic seizures.

How are clonic seizures diagnosed?

The doctor should recognize the appearance of a clonic seizure if he or she witnesses an episode. The EEG pattern will change during a seizure, so video-EEG is very useful. A factor distinguishing clonic from tonic-clonic seizures is that clonic seizures are not followed by a period of tiredness or confusion. Tonic-clonic seizures usually are.

How are clonic seizures treated?

There are medicines that can help prevent clonic seizures.

What should I do if I think my child or loved one may have clonic seizures?

If you think that you or your loved one may be having clonic seizures, talk to your child’s or loved one’s doctor as soon as possible for immediate diagnosis and treatment.

Authored by: Joseph I. Sirven, MD | Orrin Devinsky, MD on 7/2013
Reviewed by: Joseph I. Sirven, MD | Patricia O. Shafer, RN, MN on 3/2014
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