Psychoses in epilepsy: A comparison of postictal and interictal psychoses

We retrospectively analyzed data of patients with epilepsy (n = 1434) evaluated with prolonged EEG monitoring in order to estimate the prevalence of postictal psychosis (PP) and interictal psychosis (IP), to investigate a potential association of psychosis subtype with epilepsy type, and to assess differences between PP and IP. The overall prevalence of psychosis was 5.9% (N = 85); prevalence of PP (N = 53) and IP (N = 32) was 3.7% and 2.2%, respectively. Of patients with psychosis, 97.6% had localization-related epilepsy (LRE). Prevalence of psychosis was highest (9.3%) in patients with temporal lobe epilepsy (TLE). When comparing PP with IP groups on demographic, clinical, and psychopathological variables, patients with IP were younger at occurrence of first psychosis (P = 0.048), had a shorter interval between epilepsy onset and first psychosis (P = 0.002), and more frequently exhibited schizophreniform traits (conceptual disorganization: P = 0.008; negative symptoms: P = 0.017) than those with PP. Postictal psychosis was significantly associated with a temporal seizure onset on ictal EEG (P = 0.000) and a higher incidence of violent behavior during psychosis (P = 0.047). To conclude, our results support the presumption of a preponderance of LRE in patients with psychosis and that of a specific association of TLE with psychosis, in particular with PP. Given the significant differences between groups, PP and IP may represent distinct clinical entities potentially with a different neurobiological background.