Atonic Seizures

Seizures consisting of rapidly arrested movement are relatively common and account for approximately 12% of all episodes. Atonic seizure is the preferred designation for this form of clinical presentation, although more descriptive terms such as "drop attack" and "epileptic fall" are also popular. Many clinicians still use the term "akinetic seizure," but this is inaccurate because attacks of behavioral immobility with preserved muscle tone and consciousness cannot be differentiated from absence seizures. Furthermore, it is unlikely that neurophysiologic mechanisms can arrest behavior without altering muscle tone or compromising consciousness. The accurate diagnosis and management of atonic seizures constitutes an important challenge for the practicing pediatrician. Whereas grand mal and petit mal seizures are well-known manifestations of epilepsy in childhood, seizures limited to the loss of muscle tone are more likely to go unrecognized. The large variety of nonepileptic conditions that mimic atonic seizures further adds to the difficulties of correct identification. DESCRIPTION Atonic seizures show considerable variation in presentation and severity. Typically, without warning, the voluntary muscles synchronously increase and then lose resting tone. No aura precedes these muscular changes. Both the myoclonic and atonic seizure components can cause the child to collapse limply to the ground. Massive myoclonus and loss of tone may even precipitate a violent fall from a sitting position (Fig 1), resulting in craniofacial injury, skull fracture, facial laceration, or dental trauma.