Major Psychiatric Disorders Subsequent to Treating Epilepsy by Vagus Nerve Stimulation.

Purpose. The goal of this work was documentation of incidence, phenomenology, pathogenesis, and treatment of psychiatric disorders occurring subsequent to treating epilepsy by vagus nerve stimulation (VNS).Methods. In a series of 81 patients treated by VNS, all patients who developed major psychiatric complications underwent systematic psychiatric evaluation and treatment with psychotropic medication; VNS was modified if necessary.Results. After the seizure frequency was reduced by at least 75%, 7 of 81 patients (9%) developed major psychiatric disorders: Six became severely dysphoric (5 with catastrophic rage and 4 with psychotic symptoms), and one became psychotic. All 7 patients had experienced dysphoric disorders and 2 had experienced psychotic episodes prior to the VNS treatment. Five patients had frequent daily seizures prior to treatment. Remission or satisfactory improvement was achieved with psychotropic medication in 6 patients, aided by decreasing or interrupting VNS in two patients. One patient was noncompliant and suffered a fatal outcome.Conclusion. Severe interictal dysphoric disorders associated with catastrophic rage and psychotic episodes may develop on suppressing seizures by VNS in patients with previous epilepsy-related psychiatric disorders. Patients with multiple daily seizures may be more vulnerable to this occurrence. The phenomenon corresponds to the common finding of interictal dysphoric and psychotic symptoms emerging when inhibitory mechanisms predominate (alternative psychiatric disorders in the absence of seizures, or forced normalization of the EEG). The dysphoric symptom of catastrophic rage appears to occur more often on seizure suppression by VNS than by antiepileptic drugs. Psychiatric intervention, primarily with antidepressant medication, must be available to secure a good outcome; decrease of VNS may occasionally be required.