32-Channel banana-avg montage is better than 16-channel double banana montage to detect epileptiform discharges in routine EEGs

Objective We designed a study, comparing the yield of standard 16-channel longitudinal bipolar montage (double banana) versus a combined 32-channel longitudinal bipolar plus average referential montage (banana-plus), to detect epileptic abnormalities. Methods We selected 25 consecutive routine EEG samples with a diagnosis of spike or sharp waves in the temporal regions and 25 consecutive focal slowing and 50 normal EEGs. A total of 100 samples were printed in both montages and randomized for reading. Thirty independent EEG readers blinded from the EEG diagnosis were invited to participate. Results Twenty-two readers successfully completed the test for a total of 4400 answers collected for analysis. The average sensitivity to detect epileptiform discharges for 16 and 32-channel montages was 36.5% and 61%, respectively (P < 0.001). The specificity was not significantly different for 16 and 32-channel montages, 95.4% and 92.4%, respectively (P = 0.27). However more readers detected false positives on 32-channel montage compared to 16-channel montage. Conclusions 32-Channel banana-plus montage has a better yield to detect epileptic abnormalities than the 16-channel double banana montage. Significance Residents and EEG fellows could improve EEG-reading accuracy if taught on a combined 32-channel montage.