ABSTRACT
Brains of patients with epileptic seizures generate characteristic –eld potentials that can be recorded as epileptiform discharges in the electroencephalogram (EEG). Such epileptiform EEG activity is an important contributor to the electroclinical de–nition of epilepsies. Importantly, epileptiform discharges can be recorded not only during behavioral seizures, but also when patients appear asymptomatic. Depending on the duration, time of day, and inclusion of sleep recordings, such interictal EEG patterns are visible in surface EEG recordings in the vast majority of patients. Even though the absence of interictal epileptiform activity does not exclude the presence of an epileptic disorder, the sensitivity of the surface EEG is surprisingly high when considering the fact that only –eld potentials originating from the dorsolateral convexities of the brain are accessible to standard scalp recordings. Patterns of epileptiform activity historically made important contributions to the classi–cation of diseases as epilepsies, and presently contribute to their syndromatic classi–cation as focal or generalized epilepsies and particular syndromes within these groups, e.g., rolandic epilepsy or absence epilepsy.
