LAUSR

Introduction Recently, we showed that three parameters of seizure onset were pertinent in the comparison of scalp and intracranial EEG: latency (La, pattern (Pa, pattern concordance between scalp and intracranial), and location (Lo) concordance. Discrepancy in these three features was associated with inadequate seizure localization and possibly, lack of electrodes in the SOZ. We evaluated La, Pa, and Lo while individual icEEG contacts are (conceptually) omitted from analysis to assess how these parameters may help identify adequacy of the icEEG montage. Methods Seventeen patients who underwent SSIEEG evaluation were reviewed. The first three seizures of patients ( n  = 2) whose SOZ were identified on icEEG and had Engel Class 1 outcome post resective surgery were analyzed. The concordance (or discordance) of the La, Pa, and Lo parameters was assessed before and after IEEG electrodes at SOZ were omitted from analysis. Results With complete scalp and icEEG data, the three features were noted as concordant in 100% of the seizures where SSIEEG had detected the SOZ. When icEEG contacts were removed from the SOZ or from areas of seizure spread, two of the three features were discordant in 67% of seizures. La parameter was noted in 100% of seizures with discordant features while Pa and Lo features were noted in 50%. Conclusion Simultaneous scalp and intracranial EEG appear to be complementary in the analysis of SOZ in this small case series. Assessing the concordance between scalp and icEEG for the latency, pattern, and location of seizure onset may be informative in the assessment of icEEG coverage adequacy.