#7223 Greater number of peri-ictal symptoms endorsed on forced-choice questioning predicts functional/dissociative seizures in patients presenting with transient loss of consciousness

<h3>Background</h3> Transient loss of consciousness (TLOC) is one of the commonest neurological presentations. Over 90% of primary TLOC is due either to syncope, epileptic seizures, or functional/dissociative seizures (FDS). Obtaining a reliable patient and collateral history is key to diagnosis, but reporting of ictal experience is highly variable and dependent on clinician approach to history-taking. Previous research suggests that people with FDS (PwFDS) may be more likely to report multiple comorbidities, and also report a greater range of symptoms on review of symptoms questionnaires, than people with epilepsy. <h3>Method</h3> We prospectively recruited consecutive patients with a first presentation of TLOC to the Emergency Department, Acute Medical Unit, Cardiology or Neurology clinics at a single tertiary hospital for an 11-month period from February 2022 to January 2023. We invited patients to complete a brief self-administered online questionnaire regarding past medical history and peri-ictal symptoms, which we used to develop and validate a diagnostic algorithm for differentiating between syncope, epilepsy, and FDS; we report these results elsewhere. Here we report the value of number of historical items and peri-ictal symptoms endorsed as predictive of the diagnosis of FDS. <h3>Results</h3> We recruited 178 patients (134 syncope, 32 epilepsy, 12 FDS). People with FDS reported significantly more items of past medical history (median (IQR) 6 (4.5) for FDS; 3 (4) for epilepsy and 3 (4) for syncope; Kruskal-Wallis chi-squared = 15.474, df = 2, <i>p</i> &lt;0.001), and endorsed more symptoms (12 (6.75) for FDS, 6 (4) for epilepsy, 4 (5.75) for syncope; Kruskal-Wallis chi-squared = 19.729, df = 2, <i>p</i>&lt;0.001). Using total number of peri-ictal symptoms endorsed to predict FDS diagnosis yielded area under receiver-operating characteristic curve (AUC) = 0.864 (95% confidence interval 0.781–0.948); using an optimal cutoff of 9 or more symptoms reported was 91.7% sensitive and 72.9% specific for FDS. <h3>Interpretation</h3> Our results support previous research suggesting that PwFDS have higher levels of intra-ictal awareness than pwE, and that the relative dearth of ictal symptom reporting observed in response to open questioning in PwFDS may represent a deficit of recall rather than one of memory formation. Detailed history-taking can yield richer accounts of ictal subjective experience (as can other methods of interrogation under hypnosis). Symptom reporting in transient loss of consciousness is dependent upon history-taking style and expertise; further work is warranted to maximise information extracted from subjective seizure experiences.