Long-term significance of postictal psychotic episodes. II. Are they predictive of interictal psychotic episodes?

Objective: The aim of this study was to determine whether postictal psychotic episodes (PIPE) are predictive of the development of interictal psychotic episodes (IPE). Methods: This was a retrospective study of 18 consecutive adults with a partial seizure disorder and PIPE (study group) and 36 patients with a partial seizure disorder but without PIPE (control group). These two groups were compared with respect to the likelihood of developing IPE over an 8-year follow-up period and the variables operant in the development of IPE. Statistical analyses consisted of logistic regression models to identify the variables predictive of the development of IPE. Predictors included: number and location of ictal foci, seizure type, etiology, age at seizure onset, duration of seizure disorder, MRI abnormalities, and psychiatric history prior to the index video/EEG monitoring (other than PIPE). Results: Seven patients with PIPE and one control patient went on to develop an IPE. Predictors of IPE in univariate logistic regression analyses included a history of PIPE (P = 0.006), male gender (P = 0.028), and having bilateral ictal foci (P = 0.048). Significance disappeared for all of these variables when they were entered into a multivariate analysis. Conclusions: A history of PIPE may be a risk factor for the development of IPE. Yet, the disappearance of significance on multivariate analysis indicates that it is not an independent predictor.