A Case-Control Study of Aetiological Factors in Functional Seizures and Functional Motor Symptoms: Shared and Distinct Features

Background: Functional seizures (FS) and functional motor symptoms (FMS), subtypes of functional neurological disorder, may involve distinct predisposing, precipitating, perpetuating, and triggering (PPPT) factors. This study investigated potential PPPT factors in FS and FMS separately. Methods: Two hundred participants (FS=50, FMS=50, individuals with anxiety and/or depression [CC]=50, healthy controls [HC]=50) completed an in-depth medical history interview and online questionnaires to assess self-reported potential aetiological factors including traumatic/adverse life events, alexithymia, autistic traits, psychological and physical symptoms, illness perceptions, cognitive-behavioural responses, and outcome measures of general functioning, and health-related quality-of-life (HRQoL). Outcomes: Participants with FS more frequently reported traumatic/adverse events and psychopathology (e.g., dissociation, PTSD) as illness causes/precipitating factors, and sensory symptom triggers, relative to FMS and/or CCs. In contrast, participants with FMS endorsed physical illness causes/precipitating factors, and physical activity and emotion-related symptom triggers, more frequently than FS and/or CCs. Physical and dissociative symptoms were elevated, alongside reductions in HRQoL and general functioning, in FS/FMS compared to CCs/HCs. Greater current, threatening illness-related beliefs and cognitions were disclosed in FS/FMS compared to CCs. Negative associations between HRQoL, cognitive-behavioural responses, and traumatic/adverse events were also seen in FS/FMS. Interpretation: Distinct biopsychosocial factors may be involved in the development and maintenance of FS and FMS: traumatic events and psychopathology in FS, and physical illness/injury, physical functioning, and alexithymia in FMS. Unhelpful illness-related beliefs, and impacts on HRQoL and general functioning, are shared between these subtypes. The results of this study provide insight into potential subtype-specific characteristics of FS/FMS, with implications for treatment. Funding: The study is funded by an MRC Career Development Award to SP [MR/V032771/1]. This project also represents independent research part-funded by the NIHR Biomedical Research Centre at South London and Maudsley NHS Foundation Trust and King’s College London.