• complex partial seizures;
  • ictal electroencephalogram;
  • localization-related epilepsy

AbstractBackground: The authors evaluated the usefulness of scalp-recorded ictal electroencephalograms (EEG) in diagnosing the epileptogenic area in epilepsy with complex partial seizures.

Methods: The authors analyzed the ictal EEG of 395 seizures in 43 patients with complex partial seizures. Based on EEG findings the patients were classified according to the degree of localization of their onset areas. The results were then compared with neuroimaging findings.

Results: Only 10 patients fell into the category ‘discrete’, meaning that all the onset areas (as measured by ictal EEG) were localized in the same lobe of the same hemisphere. Seven patients were categorized as ‘lateralized’, meaning that all the onset areas were clearly lateralized in the same hemisphere but without consistent localization. Eleven patients were classified as ‘localized’, meaning that the onset area were localized simultaneously in bilateral same lobes, or changed consistently from one lobe in one hemisphere to the same lobe in the opposite hemisphere. The onset area could not be defined in 15 patients and these were categorized as ‘not defined’. No patient who underwent seven or more ictal recordings was categorized as discrete. However, when confined only to those patients in whom over 75% of the ictal recordings showed the same onset area, there was a high correlation between the epileptogenic lesions detected by ictal EEG and those detected by neuroimaging techniques.

Conclusions: The findings of the present study indicate that ictal EEG recordings are useful for determining the epileptogenic area in epilepsy with complex partial seizures, provided that more than 75% of the ictal recordings show the same ictal onset area.