Combining ictal surface-electroencephalography and seizure semiology improves patient lateralization in temporal lobe epilepsy

Purpose: The study goal was to assess the concordance of ictal surface-EEG and seizure semiology data in lateralizing intractable temporal lobe epilep sy (TLE) and to examine the benefits of the combined use of these two metho ds. Methods: We independently analyzed the ictal recordings and clinical sympto ms associated with 262 seizures recorded in 59 TLE patients. Each seizure w as lateralized on the basis of (i) its associated ictal surface-EEG pattern according to a predefined lateralization protocol and (ii) its associated ictal and postictal seizure semiology according to strictly defined clinica l criteria. Individual patients were also lateralized based on these data. Results: Ictal surface-EEG findings lateralized 62.6% of seizures and 64.4% of patients. Seizure semiology findings lateralized 46.2% of seizures and 78.0% of patients. There was a high degree of concordance between lateraliz ations based on these two methods, for both individual seizures and individ ual patients. Combination of the information from the two methods allowed f or lateralization in a greater proportion of both seizures (79.8%) and pati ents (94.9%). Combined EEG-seizure lateralization was concordant with the s ide of operation in 33 of 34 patients who underwent successful surgery (Eng el's surgical outcome class I/II). Conclusions: In TLE, there is a high agreement between the lateralization o f individual seizures and patients, which is based on ictal surface-EEG fin dings and seizure semiology. Furthermore, combination of these two methods improves the lateralization of individual seizures and patients. Thus, stan dardized combined EEG-seizure analysis is a valuable noninvasive tool in th e presurgical evaluation of TLE.