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Chapter 13 - Ictal and Interictal Epileptiform Electroencephalogram Patterns

Published online by Cambridge University Press:  11 October 2019

Vibhangini S. Wasade
Henry Ford Medical Group HFHS, Michigan
Marianna V. Spanaki
Wayne State University, Michigan
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According to the International Federation of Societies for Electroencephalography and Clinical Neurophysiology (IFSECN), epileptiform activity is defined as distinctive waveforms or complexes resembling those recorded in a proportion of human subjects suffering from epileptic disorders and in animals rendered epileptic experimentally.1 The suggestibility of epileptiform findings should not be considered absolute, and the patient’s clinical history should be taken into account when considering a diagnosis of epilepsy. Though the diagnosis of epilepsy can be entirely based on clinical history without evidence of epileptiform activity on the patient’s electroencephalogram (EEG), the presence of interictal discharges without an appropriate clinical history does not qualify the patient for a diagnosis of epilepsy. About 10% of patients who do not have epilepsy have been known to have nonspecific abnormalities on their EEG, and about 1% can have epileptiform interictal discharges without seizures. The incidence of such interictal activity is increased in children. Eeg-Olofsson et al. reported that 1.9% of 743 normal children had epileptiform discharges on their EEGs.2 Others report even more frequent occurrence of epileptiform abnormalities, up to 2–3%, in the pediatric population. In addition, several factors – including medications, skull defects, certain medical conditions, and artifacts from multiple sources – can modify recorded activity and ultimately render EEG interpretation abnormal.

Understanding Epilepsy
A Study Guide for the Boards
, pp. 239 - 250
Publisher: Cambridge University Press
Print publication year: 2019

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