EEG RESULTS ARE RARELY THE SAME IF REPEATED WITHIN 6 MONTHS IN CHILDHOOD EPILEPSY

Objective: To assess the reliability of interictal spike discharge in routine electroencephalography (EEG) testing in children, Method: EEG results of all children diagnosed in Nova Scotia with epilepsy onset b etween 1977-85 (excluding myoclonic, akinetic-atonic and absence) were reviewed. The results of the EEG at time of diagnosis (EEG1) were com pared with those of a second EEG (EEG2) within 6 months. Results: Of 5 04 children with epilepsy, 159 had both EEG1 and EEG2. EEG2 was more l ikely ordered if EEG1 was normal or showed focal slowing but less like ly if EEG1 contained sleep (p < 0.05), EEG1 and EEG2 were both normal in 23%, If EEG1 was abnormal, there was a 40-70% discordance for the t ype of abnormality on EEG2. Abnormalities were present on both EEG1 an d EEG2 in 67 cases, Of the 42/67 with major focal abnormalities on EEG 1, 7 had only generalized spike wave on EEG2, Of the 17/67 with only g eneralized spike wave on EEG1, 7 showed only major focal abnormalities on EEG2. Statistical testing showed low Kappa scores indicating low r eliability. Conclusions: The interictal EEG in childhood epilepsy appe ars to be an unstable test, A repeat EEG within 6 months of a first EE G may yield different and sometimes conflicting information.