Functional (dissociative) seizures in PCDH19 ‐clustering epilepsy: Clinical characteristics and diagnostic challenges

Abstract Objective Functional (dissociative) seizures (FDS) are increasingly recognized among individuals with epilepsy, intellectual disability (ID), and psychiatric disorders, but their occurrence in PCDH19‐clustering epilepsy (CE) has not been systematically described. We aimed to characterize the clinical features, diagnostic pathways, and management of FDS in individuals with genetically confirmed PCDH19‐CE. Methods We conducted a multicenter retrospective study across six tertiary European Epilepsy Centers. Individuals with genetically confirmed PCDH19‐CE and a diagnosis of FDS according to the International League Against Epilepsy (ILAE) criteria were included. Demographic, clinical, neuropsychiatric, neurophysiological, neuroimaging, and treatment‐related data were collected from medical records. Results Among 27 individuals with genetically confirmed PCDH19‐CE, eight (29.6%) experienced FDS. The median age at FDS onset was 16 years. Most affected individuals had some degree of ID, and nearly all exhibited psychiatric comorbidities, particularly behavioral dysregulation and autism spectrum disorder. Six patients were initially misdiagnosed with epileptic seizures, resulting in unnecessary antiseizure medication (ASM) escalation and hospitalizations. Following FDS diagnosis, ASM reduction or modification was undertaken in three patients. Multidisciplinary management involving psychiatry, psychology, and occupational therapy was implemented in most cases, and all treated individuals demonstrated clinical improvement. Significance FDS may constitute an important comorbidity in individuals with PCDH19‐CE, particularly during adolescence and adulthood. Early recognition of FDS may prevent unnecessary diagnostic and therapeutic interventions, reduce inappropriate ASM escalation, and improve patient outcomes through timely multidisciplinary care.