Subjective seizure symptom reporting in functional/dissociative seizures and epilepsy: Effects of sampling technique and patient characteristics.

BACKGROUND:Differences in subjectively reportable ictal experiences between epilepsy and functional/dissociative seizures (FDS) have received less attention than visible manifestations. Patients with FDS (pwFDS) tend to report seizure symptoms differently than patients with epilepsy (pwE). The effects of symptom elicitation method and mediation by psychopathological traits have not been examined and may aid in differentiating the disorders. METHOD:Analysis of responses of 24 pwE and 28 pwFDS in interviews exploring ictal experiences through open questioning followed by structured closed questioning using possible symptom prompts (74-item modified Psychosensory-Psychomotor Phenomena Interview, PPPI); self-report of psychological profile (HADS-A, HADS-D, PHQ-15, DES-T, THQ, PCL-C). RESULTS:Symptom prompting with PPPI elicited three times more seizure symptoms than open questions in pwE (median 34 vs. 11.5, p = 0.005) and over four times more in pwFDS (42.5 vs. 11, p = 0.001). Intra-ictal symptoms were reported freely more frequently by pwE (median 6.5 vs. 4, p = 0.005), while pwFDS reported more pre-ictal symptoms after prompts (median 6 vs 14.5, p = 0.004). The difference between freely reported and PPPI-elicited symptoms correlated with different psychopathological traits in pwE and pwFDS. Symptoms of anxiety (HADS-A) correlated more strongly with prompted symptoms among pwE than pwFDS (z = 2.731, p = 0.006). CONCLUSION:Prompting generates more detailed ictal symptom profiles than simply encouraging patients to narrate their subjective seizure experiences. While pwFDS freely reported fewer symptoms related to the intra-ictal period compared to pwE, pwFDS reported more pre-ictal symptoms than pwE when prompted. Differences in the psychopathological traits associated with the number of peri-ictal symptoms captured by symptom prompting in pwE and pwFDS possibly reflect etiological or psychological differences between these patient groups.