Abstracts

Rationale: Epidemiologic studies are necessary to define the public health burden of epilepsy within a population, to provide information needed for early detection and treatment, and to set public health and health care priorities (1). Seizures and epilepsy are subject to misdiagnosis and there is a lack of published information on the incidence of ‘seizure mimics’ within any population. The International League Against Epilepsy (ILAE) updated the definition of epilepsy in 2014 (2) such that a person can be diagnosed with epilepsy following a single seizure if their risk of recurrent seizures is approximately 60% or more, whereas the 1993 (3) definition required two or more unprovoked seizures. No epidemiologic study to date has reported the application of this definition to a defined population, or the incidence of seizure mimics within a population. Methods: We applied multiple overlapping retrospective and prospective methods of case ascertainment to a defined geographical area (population 542,868) from 1st January 2017 to 31st December 2017 to identify all first seizures (both provoked an unprovoked), new diagnosis of epilepsy and seizure mimics who first presented during the calendar year 2017. Seizure mimics were defined as cases in whom a working diagnosis of seizure was considered, but in whom an alternate diagnosis was subsequently reached. We applied the 1993 (3) and 2014 (2) ILAE definitions of epilepsy to all definite and probable new diagnosis of epilepsy. Results: The incidence of all first seizures was 102 per 100,000 per year (age standardized 124), and the incidence of seizure mimics was 92 per 100,000 per year (age standardised 111). Both displayed a bimodal age- specific incidence with highest incidence in the youngest and oldest age groups, Figure 1. The most frequently encountered seizure mimic was syncope (52%, n=263). According to the 2014 (2) ILAE definition of epilepsy, the incidence of new diagnosis of epilepsy was 62 per 100,000 per year (age standardised 75). When the 1993 (3) definition was applied to the same population, the incidence was 41 per 100,000 per year (age standardised 49), Figure 2. Conclusions: The incidence of seizure mimics was almost equal to that of all first seizures. Application of the 2014 (2) ILAE definition of epilepsy resulted in an approximate 50% increase in the incidence of new diagnosis of epilepsy compared to the 1993 (3) definition. Seizures, epilepsy and seizure mimics represent a significant burden to health care systems.1. Thurman DJ, Beghi E, Begley CE, et al. Standards for epidemiologic studies and surveillance of epilepsy. Epilepsia 2011; 52 Suppl 7: 2-26.2. Fisher RS, Acevedo C, Arzimanoglou A, et al. ILAE official report: a practical clinical definition of epilepsy. Epilepsia 2014; 55(4): 475-82.3. Commission on Epidemiology and Prognosis, Internatinoal League Against Epilepsy. Guidelines for epidemiologic studies on epilepsy. Epilepsia 1993; 34(4): 592-96. Funding: No funding