EEG features of cortical dysplasia in children.

Two distinctive electroencephalographic abnormalities, very high amplitude rhythmic activity or prominent fast activity, have been described in children with extensive cortical dysplasia. Cases with cortical dysplasia identified on computerised tomography or magnetic resonance imaging, or a characteristic EEG were selected. One hundred and forty electroencephalograms from 94 cases were reviewed and related to the imaging findings. An EEG with very high amplitude rhythmic activity was found to have high specificity for severe cortical dysplasia but low sensitivity (< 50% cases). Abnormal fast activity was not specific and was seen with very diverse pathologies. The EEG features of most cases with localised cortical dysplasia were very variable. The EEG could be normal even when the cortical dysplasia was extensive.