An atonic seizure is a sudden loss of muscle tone in the muscles that
hold the body and head upright.
The seizure occurs without warning and usually
causes the person to fall down.
Some atonic seizures may be more
limited, only causing the person's head to drop for a moment.
Atonic seizures are fairly uncommon and occur mostly in people with
Lennox-Gastaut syndrome. This is a severe form of generalized epilepsy that begins
in early childhood. (Children with Lennox-Gastaut syndrome may also have
People who have atonic or tonic seizures are likely to be injured
when they fall. Children may have to wear helmets and restrict their activities
to prevent serious injury.