Phenotyping of Review-of-Systems Responses to Differentiate Functional Seizures From Epilepsy

Objective: Although the populations of patients with functional seizures (FS) and epileptic seizures (ES) are extremely heterogeneous with multiple etiologies and phenotypes, patients with FS have increased somatic sensitivity and report more positive complaints on review-of-systems questionnaires (ROSQs). We evaluated if data-driven clustering and projection analysis could identify symptom phenotypes that could differentiate between patients with FS and ES.

Methods: The dataset included all adult patients admitted from January 2006 to March 2020 for video-electroencephalography with available ROSQs (N = 877). Latent clusters and axes of variation in ROSQ responses were evaluated using multiple well-established methods. Leave-one-out cross-validation was used to evaluate if logistic regression using information could differentiate patients with FS from ES.

Results: When evaluating individual symptom response and proportion of positive responses, the area under the receiver operating curve (AUC) was 62% (95% CI, 53%-69%) and 72% (CI, 65%-78%), respectively. The best AUC achieved by phenotyping methods was 74%. The patterns of clusters and components reflected properties of each analysis and did not correlate with assigned "system" from the ROSQ or other interpretations.

Discussion: The overall proportion of positive responses was the most informative metric to differentiate patients with FS compared to ES. While both FS and ES are heterogeneous populations with multiple subgroups, these subgroups were not meaningfully identified based on ROSQ symptoms. The limited overall predictive accuracy and AUC suggests that, in absence of other supporting data, ROSQ responses in patients with FS and ES were not clinically useful for screening.