Interictal regional paroxysmal fast activity on scalp EEG is common in patients with underlying gliosis

The morphology and the distribution of interictal epileptiform discharges (IEDs) on scalp EEG provide useful information about the syndromic diagnosis of epilepsy and its localization in cases of focal epilepsy (Niedermeyer, 1999). Traditionally, IEDs are considered to have a limited specificity with regard to the underlying etiology of epilepsy. However, certain EEG patterns in the form of continuous or semi-continuous rhythmic IEDs and interictal regional polyspikes on intraoperative electrocorticography and scalp EEG have been demonstrated more commonly in patients with focal cortical dysplasia (FCD) (Ferrier et al., 2006; Gambardella et al., 1996; Noachtar et al., 2008; Palmini et al., 1995; Rosenow et al., 1998).

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