Does intraoperative electrocorticography alter seizure outcomes after temporal lobe epilepsy surgery?

Surgery is the treatment of choice in drug-resistant temporal lobe epilepsy (TLE). The estimated seizure freedom after anterior temporal lobectomy and amygdalo-hippocampectomy (ATL-AH) is 70%-80%. Accurate identification of the epileptogenic zone by prompt presurgical evaluation reduces surgical failures. Our study aims to assess the utility of intraoperative electrocorticography (iECoG) in improving seizure outcomes following ATL-AH.

We enrolled patients with drug-resistant TLE who underwent ATL-AH from January 2009 to December 2018. They were followed up at 3 months, 12 months and annually for assessment of seizure recurrence. Post-resection ECoG findings were classified into (1) no/rare residual epileptiform discharges and (2) less than 50% reduction in discharges. Post-operative outcome was deemed "good" if seizure-free and aura-free during the entire period of post-operative follow-up and "poor" if there is a recurrence of auras and/or seizures.

Among the 684 patients enrolled, 566 had "good" outcomes and 118 had "poor" outcomes. Resection was ECoG-guided in 545 patients. Less than 50% reduction in spikes on post-resection ECoG was found in 133 patients. There was no significant difference in seizure outcomes based on ECoG guidance (p = 0.65) or clearance of spikes on post-resection ECoG (p = 0.13). iECoG was not done in 139 (20.3%) patients due to technical glitches during the procedure or due to affordability issues.

Utility of iECoG in tailoring resection margins is limited and it does not predict seizure outcome after ATL-AH. In centers where ATL-AH is ECoG-guided, it is advisable to abandon this time-consuming procedure.