Impairment of ictal consciousness and psychosis in drug‐resistant focal epilepsy: A retrospective clinical cohort study

Objective: Psychoses of epilepsy (POE) affect up to 13% of patients with focal epilepsy. Whereas interictal risk factors are well documented, ictal correlates of POE remain poorly characterized. We hypothesized that an impairment of ictal consciousness on the Consciousness Seizure Scale (CSS), would be associated with POE. We assessed the association between ictal clinical features and POE compared to non-POE in adults with drug-resistant focal epilepsy.

Methods: We retrospectively analyzed a presurgical cohort of adults with drug-resistant focal epilepsy monitored by video-electroencephalography (EEG) or stereo-EEG. For each patient, all seizures with an examination allowing the completion of CSS score were included. POE were identified through standardized psychiatric interviews. Association between ictal features, primarily CSS score, and POE was tested using generalized estimating equations (GEE).

Results: Among 232 included seizures (25 from POE group, 207 from non-POE group), the probability of POE varied nonlinearly with ictal consciousness; it peaked at intermediate CSS scores (GEE, OR = 4.31, p = .006). This effect remained after adjustment for duration of both epilepsy (OR=1.06, p = .005) and seizure (OR=1.20, p = .013). Intraclass correlation of CSS was .76 (95%CI, .65-.85), reflecting a low within-patient variance. An older age, more severe depressive and anxiety symptoms were also associated with POE.

Significance: POE were associated with intermediate impairment of ictal consciousness, suggesting that partial disruption of awareness may favor the emergence of psychotic symptoms. The high level of intrapatient stability for CSS, mostly estimated from non-POE, suggests that CSS could be constant across seizures. This raises the possibility that POE risk could stem from the way consciousness is altered during seizures.