Semiology of functional/dissociative seizures in idiopathic generalized epilepsy: An inpatient video‐electroencephalographic study

OBJECTIVE: This study was undertaken to estimate the prevalence and characterize the semiology of co-occurring functional/dissociative seizures (FDSs) and identify clinical features potentially associated with the development of video-electroencephalography (video-EEG)-diagnosed FDSs in patients with idiopathic generalized epilepsy (IGE). METHODS: In this retrospective single-center inpatient video-EEG study, we characterized clinical features of FDSs recorded in patients with IGE aged ≥16 years admitted into our epilepsy monitoring unit between January 2008 and December 2024. We compared clinical characteristics of IGE patients with FDSs to an IGE cohort without FDSs. FDSs were classified as akinetic nonmotor, subjective nonmotor, motor, or mixed FDSs. RESULTS: Among 123 patients with IGE, 29 (23.5%) had co-occurring documented FDSs recorded on video-EEG. Twenty-eight (96.5%) were females. Median age at admission was 25 years (interquartile range [IQR] = 14). The median length of admission was 5 days (IQR = 3). Twenty-eight patients (96.5%) had generalized interictal discharges, emerging on the first day of admission in 24 of 28 (85.7%). Epileptic seizures were also captured in 13 patients (44.8%). Twenty-four patients (82.7%) had multiple FDSs episodes, whereas 19 (65.5%) presented with a single FDSs subtype. Subjective FDSs was the most common subtype (17/29, 58.6%), followed by pure motor (6/29, 20.7%), mixed motor-akinetic (6/29, 20.7%), pure akinetic (5/29, 17.2%), mixed akinetic-subjective (4/29, 13.8%), and mixed motor-subjective (1/29, 3.4%). Among the clinical variables analyzed, female sex was associated with co-occurring FDSs, although this association did not remain significant after Bonferroni correction. SIGNIFICANCE: Approximately one quarter of patients with IGE who underwent video-EEG had co-occurring FDSs. Almost half had epileptic seizures during the same admission. Video-EEG referral should be considered in patients with suspected drug-resistant IGE with active seizures or if there is a clinical suspicion of FDSs.