Seizure Outcome of Patients with Magnetic Resonance Imaging–Negative Epilepsies: Still An Ongoing Debate

Background Surgical results regarding MRI-negative epilepsy were presented and related clinical and histopathological parameters were discussed. Methods Thirty-six MRI-negative epilepsy patients were retrospectively analyzed. Histopathological specimens were re-reviewed by 2 blind neuropathologists and re-classified based on the current classifications. Results The mean age at surgery and seizure onset was 24.5 years and 9.3 years, respectively. Eight patients were younger than 18 years. Mean duration of seizures was 15.3 years. All but 2 underwent invasive monitorization. Eighteen patients had hypometabolism on FDG-PET with temporal lobe involvement in majority (66.7%). Hypometabolism was found in all patients with hippocampal sclerosis (HS), which was present in 50% and 66.7% of focal cortical dysplasia (FCD) type I and II patients, respectively. The frontal lobe resection was the most frequent type of operation followed by resections in temporal, parietal and occipital lobes. In 7 patients, multilobar resection was performed. Histopathological diagnosis was FCD type I, II, III, HS, and gliosis in 14, 12, 2, 3 and 2 patients, respectively. The mean follow-up was 5.8 years. Seventeen patients were seizure free and favorable outcome (Engel's I and II) was found in 69.7%. FCD type I tend to have more favorable seizure outcome. Duration of epilepsy and hypometabolism on FDG-PET was significantly related to outcome, whereas involved lobe was not. Conclusions Our results suggest it is worth pursuing resective surgery in adults as well as in children with drug-resistant epilepsy with normal MRI.