Absence Seizure

Absence Seizure

Absence seizures are one of several kinds of seizures. These seizures are sometimes referred to as petit mal seizures (from the French for "little illness", a term dating from the late 18th century).

Absence seizures are brief (usually less than 20 seconds), generalized epileptic seizures of sudden onset and termination. They have two essential components:

• clinically, the impairment of consciousness (absence)
• Electroencephalography (EEG) shows generalized spike-and-slow wave discharges.

Absence seizures are broadly divided into typical and atypical types. Typical absence seizures usually occur in the context of idiopathic generalised epilepsies and EEG shows fast >2.5 Hz generalised spike-wave discharges. The prefix “typical” is to differentiate them from atypical absences rather than to characterise them as "classical" or characteristic of any particular syndrome.

Atypical absence seizures:

• occur only in the context of mainly severe symptomatic or cryptogenic epilepsies of children with learning difficulties who also suffer from frequent seizures of other types, such as atonic, tonic and myoclonic.
• onset and termination is not so abrupt and changes in tone are more pronounced.
• ictal EEG is of slow less than 2.5 Hz spike and slow wave. The discharge is heterogeneous, often asymmetrical and may include irregular spike and slow wave complexes, fast and other paroxysmal activity. Background interictal EEG is usually abnormal.