Typical absences

Introduction
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By C P Panayiotopoulos MD PhD

Typical absence seizures (previously known as petit mal) are brief (seconds in duration) generalized epileptic seizures of abrupt onset and abrupt termination. They have 2 essential components: (1) clinically, the impairment of consciousness (absence) and (2) EEG generalized 3 to 4 Hz (less than 2.5 Hz) spike-and-slow wave discharges. Typical absences are clusters of clinico-EEG manifestations that may be syndrome related. Absences may be the only type of seizures occurring in the patient, as in childhood absence epilepsy, or may be mild and nonpredominant, as in juvenile myoclonic epilepsy. Typical absences are fundamentally different and pharmacologically unique compared to any other type of seizures, which also makes their treatment different. Antiepileptic drugs effective for focal seizures may be deleterious for absence seizures. In this clinical summary, Dr. C P Panayiotopoulos, Consultant Emeritus in Clinical Neurophysiology and Epilepsy at St. Thomas’ Hospital in London, England, details developments in the pathophysiology, genetics, and pharmacological treatment of absence seizures and related epileptic syndromes.

Key Points

  • Typical absence seizures (previously known as petit mal) are brief (seconds in duration) generalized epileptic seizures of abrupt onset and abrupt termination.
  • The defining manifestations of typical absence seizures are impairment of consciousness and generalized 3 to 4 Hz spike-wave discharges.
  • Typical absences are fundamentally different and pharmacologically unique compared to any other type of seizures, which also makes their treatment different.
  • The clinico-EEG manifestations of absence seizures are syndrome-related. Childhood and juvenile absence epilepsy are the archetypal syndromes of typical absences.
  • Typical absences, particularly in adults, are frequently misdiagnosed as focal seizures with detrimental effect on patient management.
  • Antiepileptic drugs effective for focal seizures may be deleterious for absence seizures.

In This Article

Introduction
Historical note and nomenclature
Clinical manifestations
Localization
Pathophysiology
Epidemiology
Differential diagnosis
Underlying disorders
Diagnostic workup
Management
References cited
Contributors