Two-Year Follow-up Outcomes of Non-lesional Epilepsy Surgery in Iran

Background: Despite treatment with anti-epileptic drugs, 30% of epileptic patients continue to experience seizures, makingsurgery a viable option. Surgery has shown efficacy even in non-lesional epileptic individuals, although there is limited researchon this topic. Objectives: This study aimed to investigate surgical outcomes in individuals with drug-resistant epilepsy (DRE) who undergosurgery despite having non-lesional magnetic resonance imaging (MRI) findings. Methods: This observational longitudinal study was conducted between 2017 and 2020 at a referral hospital in Tehran, Iran.Using census sampling, we screened 750 epilepsy cases and enrolled 80 patients (42 women and 38 men) with DRE and non-lesional MRI findings who underwent epilepsy surgery. We collected patients' demographics and seizure characteristics. A 2-yearfollow-up was conducted to assess the seizure freedom rate. We compared seizure-free and non-seizure-free patients whounderwent temporal epilepsy surgery, extratemporal epilepsy surgery, corpus callosotomy, and Vagus nerve stimulation (VNS)using chi-square, Fisher exact, and binary logistic regression tests. Results: The seizure freedom rate was 62.7% for temporal surgery, 83.33% for extratemporal surgery, 26.66% for corpuscallosotomy, and none for patients who underwent VNS. There was no difference between seizure-free and non-seizure-freepatients in terms of their baseline characteristics, seizure semiology, lesion features, and post-operative findings (P-values >0.05), except that patients without a history of febrile convulsions tended to experience more seizure freedom afterextratemporal surgery (P = 0.007). Additionally, older patients tended to experience more seizure freedom after temporalsurgery (P = 0.03). Conclusions: This study underscores the potential benefits of epilepsy surgery in non-lesional DRE patients. Further research isneeded to establish criteria for patient selection in this context.