Atonic (astatic) seizures, or drop attacks, are characterized by a sudden loss of muscle tone. They begin suddenly and without warning. There may be total lack of tone, so that the person will fall quickly to the floor and cannot protect himself or herself against injury. Consciousness is impaired during the fall, although the patient may regain alertness immediately upon striking the floor.

Some atonic seizures may be fragmentary and lead to dropping of the head with slackening of the jaw or dropping of a limb.

Electromyographic activity is lost during atonic seizures.

Atonic seizures are rare and are usually confined to childhood. Most children with drop attacks also have myoclonic or tonic seizures. Most of these children have the Lennox-Gastaut syndrome.

Atonic attacks are often associated with myoclonic jerks either before, during, or after the atonic seizure. This combination has been described as myoclonic-astatic seizures.

Electroencephalography

Atonic seizures are usually associated with rhythmic spike-and-wave complexes varying from slow (1 to 2 Hz) to more rapid, irregular spike- or multiple spike-and-wave activity.

Authored By: 
Gregory L. Holmes MD
MD
I<
Authored Date: 
01/2004