Accuracy of seizure detection using abbreviated EEG during polysomnography

The purpose of this study was to determine the validity of abbreviated EEG montages for seizure detection during polysomnography. Three electroencephalographers reviewed files containing seizures or nonepileptic events using 8- and 18-channel montages. Files were rated as to whether they contained seizures and assigned a "probability of seizure" score from 0% to 100% reflecting the confidence that it was a seizure. Readers then localized seizures as temporal, frontal, parieto-occipital, or nonlocalized and provided a probability of correct localization with 0% to 100% confidence. Data were analyzed using the Adjusted McNemar Test method of Obochuwski. The probability of seizure score was measured using the receiver operating characteristic curve. Observed agreement was 78% and 84% for 8- and 18-channel montages, respectively. Readers were better able to distinguish seizures from nonepileptic events using the 18-channel montage (P = 0.004). Seizures localized to the temporal and parieto-occipital regions were more likely to be correctly identified and localized. Readers were able to correctly localize 27% and 49% of seizures using the 8- and 18-channel montages, respectively (P < 0.001). Abbreviated EEG montages are inadequate in the differentiation of seizures and nonepileptic events arising from sleep during polysomnography. This seems to be particularly true in frontal lobe epilepsy.