Intracranial EEG findings and outcomes in MRI-negative epilepsy with temporal lobe semiology and scalp EEG features

We sought to correlate seizure and cognitive outcomes with seizure onset zones (SOZs) determined from intracranial EEG (iEEG) in patients with MRI-negative drug-resistant focal epilepsy with scalp EEG and semiological features of temporal lobe epilepsy (TLE). We identified 66 patient cases with these imaging, EEG, and semiological characteristics evaluated at the Medical College of Wisconsin from 2002 to 2024. Ictal iEEG data were available for 61 patients. Of these, 25 (41%) had unilateral SOZs in the anteromedial temporal lobe (Group A). In 36 (59%) patients SOZs were in the mid to posterior temporal neocortex, adjacent/closely connected regions (temporal-plus), entirely extratemporal, or involved both temporal lobes (Group B). In all, 45 patients underwent resective surgery, with a significantly higher proportion of patients in Group A (84%) undergoing resection compared to Group B (58%) (p = 0.049). Overall, 40 (88%) had an Engel I outcome at last follow up (11.5 years +/- 5.91). Seizure-outcomes were transiently superior in Group A at year-1 post-surgery (p = 0.048), but there was no significant difference at year-2 or at last follow up between the two groups. Postoperative neuropsychological data were available for 28 patients (14 each in Group A and B) and notable only for an improvement in processing speed index (PSI) in Group A and a decline in Group B (p = 0.015). Our results indicate that with carefully planned iEEG studies to guide tailored resections, excellent long-term post-surgical outcomes can be achieved in most MRI-negative epilepsy patients with temporal lobe semiology and scalp EEG features.