Reliability of seizure semiology in patients with 2 seizure foci

Objective: To determine whether seizure semiology is reliable in localizing and distinguishing seizures at 2 independent brain foci in the same patient. Design: Two masked reviewers localized seizures from 2 foci by their clinical semiology and intracranial electroencephalograms (EEGs). Setting: Epilepsy monitoring unit of referral comprehensive epilepsy program. Patients: Seventeen consecutive patients (51 seizures) with sufficient video and intracranial EEG data were identified by reviewing medical records of 366 patients older than 10 years. Main Outcome Measures: The primary outcome measures were interobserver agreement between the 2 masked reviewers; the proportion of seizures localized by semiology; the proportion of localized seizures concordant with intracranial EEG localization; and comparison between concordant and nonconcordant seizures in latency of intracranial EEG seizure spread. Results: Interobserver agreement was 41% (κ score, 0.16). Only 30 of 51 seizures (59%) were localized by seizure semiology. The focus localized by semiology was concordant with the location of intracranial EEG seizure onset in 16 of 30 seizures (53%). No significant difference was observed between concordant and nonconcordant seizures in relation to the speed with which the EEG discharge spread from the location of seizure onset to another lobar region (P=.09, Wilcoxon rank sum test). Conclusion: Clinical seizure semiology is not as useful as intracranial EEG in localizing seizure onset in patients with dual seizure foci.