CAN SLOW WAVES IN THE ELECTROCORTICOGRAM (ECOG) HELP LOCALIZE EPILEPTIC FOCI

In patients operated for medically refractory epilepsy, ECoGs are often performed to help further localize the epileptogenic focus. During the necessarily short recording, spikes may be rare or absent, or may be only a partial representation of the epileptic activity. The usefulness of background abnormality in localizing the focus in ECoGs was therefore determined. The relationships of MRI, CT, and pathological findings with ECoG background were also noted. The ECoGs of 40 patients were recorded. Delta activity was evaluated by spectral analysis. In 22 ECoGs, maximum delta activity rarely conincided spatially with maximum spiking or was adjacent to it. The region of maximum delta activity rarely coincided with CT, MRI and pathological findings. Although the relationship between delta activity and spiking was much stronger than expected by chance, it may not be sufficient to allow the use of delta activity to localize a focus in individual cases. © 1990.