Value of seizure semiology and ictal source analysis in lateralizing and localizing the epileptic zone

BackgroundSophisticated analysis of seizure semiology and electroencephalography (EEG) has a significant role in lateralizing and localizing the epileptogenic zone. Hence, understanding the pathophysiology of epileptogenic dysrhythmia requires thorough knowledge of how to put the very different pieces of the puzzle together.ObjectiveThe aim of the study was to investigate the concordance between seizure semiology, electrophysiological generator, anatomical lesions, and neuropsychological evaluation in patients with partial epilepsy, and to identify the importance of ictal EEG recording and the diagnostic yield of other electrophysiological techniques.Patients and methodsThirty patients with a diagnosis of intractable partial epilepsy and lesional MRI were prospectively included. All of them were clinically evaluated and identified according to semiological seizure classification. Long-term video digital EEG with ictal recording was done, along with a source analysis (SA) study.ResultsClinical evaluation by seizure semiology lateralized 73% of the cases and localized 80%. Ictal EEG lateralized 80% of cases and localized 66.9%. SA revealed a much superior power to lateralize and localize (96.7%) the epileptogenic zone, but what is more important is the added value of SA, as it lateralized and localized 96-100% of the cases that failed on semiology. SA has the highest expected value for additional lateralizing and localizing information ( ±7.73 and ±7.30, respectively).ConclusionSeizure semiology and ictal EEG recording with SA are the most accurate ways to lateralize and localize the epileptogenic zone in intractable partial epileptic cases, giving the patient a respectable chance to avoid other invasive diagnostic techniques.