Abstracts

Rationale: Previous studies analyzing the National Inpatient Sample (NIS) have shown that the number of epilepsy surgeries in the US have remained relatively stable. Since the NIS is derived from a random sample of only 20% of all hospital discharges, there is concern that the NIS may not provide an accurate enough estimate of the number of epilepsy surgeries. More importantly, the NIS contains only diagnosis and procedure codes; identification of specific surgical procedures has not been feasible. As a result, temporal patterns of specific epilepsy surgery utilization in the US remain largely unknown. Every year the National Association of Epilepsy Centers (NAEC) asks its members to provide information on the level of care provided to epilepsy patients including the number of epilepsy surgeries to indicate whether individual epilepsy centers meet criteria for level 3 or level 4 (most advanced) designations. We used data from the NAEC s annual survey to analyze utilization of epilepsy surgery, particularly anterior temporal lobectomy (ATL) for straightforward mesial temporal sclerosis (MTS) in the US.Methods: We obtained annual NAEC designation surveys between 2003 and 2010 from the NAEC. The survey was designed based on the NAEC s guidelines for essential services, personnel, and facilities in specialized epilepsy centers. We calculated annual rates of total numbers of surgeries and ATL for MTS based on the US Census population estimates and the prevalence rate of 7.1/1,000 persons. The number of people with refractory epilepsy (PWRE) was estimated to be approximately 30% of the entire epilepsy population. Since up to 20% of PWRE turn out to be non-epileptic cases, only 80% of the total number of PWRE was used as a denominator to calculate rates for comparison over time.Results: The number of epilepsy centers that responded to the annual survey increased from 37 in 2003 to 129 in 2010. We noted an increase in the overall epilepsy surgeries from 363.5/100,000 PWRE during 2004-2006 to 568.9/100,000 PWRE in 2007-2010. Given an increase in the number of epilepsy centers, the average number of epilepsy surgeries performed in each epilepsy center remained relatively stable during the study period (26 cases per center in 2004-2006 to 27 cases per center in 2007-2010). In contrast, the number of ATL for MTS decreased from 170.9/100,000 PWRE during 2003-2006 to 124.1/100,000 PWRE in 2007-2010. The average number of ATL for MTS performed in each epilepsy center also significantly decreased from 14 cases per center in 2003-2006 to 6 cases per center in 2007-2010. Conclusions: In contrast to previous reports, we find that the number of epilepsy surgeries in the US have increased over time, correlating with an expansion of NAEC member epilepsy centers. Despite an increase in the number of epilepsy surgeries, the number of ATL for straightforward MTS have been decreasing significantly over time. Given the current rate of operations, and given epidemiological projections, epilepsy surgery remains an underutilized option for persons with intractable epilepsy.