Quantitative peri-ictal electrocorticography and long-term seizure outcomes in temporal lobe epilepsy

• Temporal lobe epilepsy was followed over a mean of 50 months for seizure outcome.
• Theta activities between −10 and −5 s from the ictal onset were significant.
• Delta, beta and alpha activities were significant before multiple comparison corrections.
• Pre-ictal activity >200 μV tended to be common in the seizure-free group.
• Pre-ictal activity >350 μV was more common in the cortical dysplasia type I group.

SummaryWe analyzed peri-ictal electrocorticography below 70 Hz by a semiautomatic quantitative method. Thirty-four patients with medically intractable temporal lobe epilepsy underwent chronic electrocorticography using subdural electrodes. The resection extent of cortices with maximum amplitude activities were compared between seizure outcome groups. In detected activity significantly related to seizure outcome, we analyzed waveforms with automated waveform amplitude analysis. Mann–Whitney U tests were used. Mean follow-up duration was 49.7 ± 18.2 months. The resection extents of maximum amplitude activities in theta bands during the period between −10 and −5 s from the ictal onset were significantly different between seizure outcome groups (adjusted p = 0.01, the Benjamini–Hochberg correction). Delta, alpha and beta bands were related to seizure outcome only without multiple comparison corrections (unadjusted p = 0.02, 0.03 and 0.04). Waveform peak amplitudes greater than 200 μV tended to be more common in the seizure free group than in the non-seizure-free group (unadjusted p = 0.06). Waveform peak amplitudes greater than 350 μV were significantly more common in the cortical dysplasia type I group than in the hippocampal sclerosis group (unadjusted p = 0.03). The resection of theta band activities during the preictal period was most important for good seizure outcome in temporal lobe epilepsy.