TMS-EEG in postictal psychosis of epilepsy

Background: Postictal psychosis (PIP) is a poorly understood complication affecting 2 % of individuals with epilepsy. Genomic and neuroimaging studies suggest parallels with schizophrenia. Objectives: To determine whether Transcranial Magnetic Stimulation coupled with Electroencephalography (TMS-EEG), can reveal schizophrenia-like changes in PIP, especially in Natural Frequency (NF), gamma band Event-Related Spectral Perturbation (ERSP), the N100 peak, and global mean field power (GMFP). Methods: We applied TMS-EEG targeting the non-dominant hemisphere premotor area in people with focal epilepsy (PWE) with a history of PIP (n = 7) and PWE without any history of psychosis (n = 14). Two-tailed t-tests were applied to TMS-EEG metrics previously studied in schizophrenia to look for differences between the groups, with subgroup analyses excluding participants using benzodiazepines. Results: Demographic and clinical characteristics were similar across the two groups. No significant differences were seen in NF (p = 0.98). We observed a delayed N100 peak latency in the PIP group when excluding those with regular benzodiazepine use (p = 0.05) and increased global mean field power during the 400-600 ms phase of the TEP (p = 0.02). Mean ERSP within the gamma band was lower in the PIP group, though this did not reach statistical significance (p = 0.08). Conclusion: This is the first study to apply TMS-EEG in individuals with PIP, demonstrating feasibility and providing methodological insights for future studies. Preliminary findings, including increased GMFP and delayed N100 latency in PIP, suggest possible disruptions in cortical excitability similar to schizophrenia, warranting further investigation.