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

Abstract

The study goal was to assess the concordance of ictal surface-EEG and seizure semiology data in lateralizing intractable temporal lobe epilepsy (TLE) and to examine the benefits of the combined use of these two methods. We independently analyzed the ictal recordings and clinical symptoms associated with 262 seizures recorded in 59 TLE patients. Each seizure was 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 clinical criteria. Individual patients were also lateralized based on these data. 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 lateralizations based on these two methods, for both individual seizures and individual patients. Combination of the information from the two methods allowed for lateralization in a greater proportion of both seizures (79.8%) and patients (94.9%). Combined EEG-seizure lateralization was concordant with the side of operation in 33 of 34 patients who underwent successful surgery (Engel's surgical outcome class I/II). In TLE, there is a high agreement between the lateralization of individual seizures and patients, which is based on ictal surface-EEG findings and seizure semiology. Furthermore, combination of these two methods improves the lateralization of individual seizures and patients. Thus, standardized combined EEG-seizure analysis is a valuable noninvasive tool in the presurgical evaluation of TLE.