Vagus nerve stimulation as a potential modulator of periictal psychotic episodes: A report of four cases.

Abstract Drug resistant epilepsy (DRE) has been associated with a high incidence of psychotic disorders. Patients can develop psychosis after starting a new antiseizure medication, after undergoing resective surgery, or after implantation of a vagus nerve stimulation (VNS) system. The aim of this study was to investigate the modulation effect of VNS on psychotic episodes in DRE patients with a pre-existing history of periictal psychotic episodes (PPE). We retrospectively report the outcome of four patients from a single tertiary centre with PPE prior to implantation. None of the implanted patients developed de novo PPE after VNS therapy. Regarding seizure outcome, all patients were responders: two of them (50%) stopped suffering status epilepticus and three (75%) showed seizure characteristic changes after VNS implantation. PPE disappeared in all patients: in two of them (50%) at 6 months post-implantation and in the others (50%) at 2 and 3 years, respectively. 18F-FDG-PET results showed hypermetabolism in both anterior insular and medial frontal lobes which disappeared in the 18F -FDG-PET 4 years post-implantation. Based on the results of this series of cases we suggest that VNS therapy could potentially act to alleviate PPE in patients with DRE, but its effectiveness may be time-dependent.