Abstracts

Rationale:
The prevalence of epilepsy in multiple sclerosis (MS) is 3-7 times higher than in the general population. Patients with MS and focal epilepsy (MS+E) have higher mortality and faster cognitive decline than those with either MS or epilepsy alone. However, it is unclear if the overall severity of epilepsy in MS+E is higher than in other focal epilepsies as defined by healthcare utilization, the incidence and duration of status epilepticus (SE), and the need for antiseizure medication (ASM) regimen changes (as an attempt to better control seizures and/or to improve ASM tolerability).
Method:
We analyzed un-identifiable claims data from a nationwide US health insurance plan. For the study period (1/2008 - 8/2019), the dataset included > 86 million individuals. We used International Classification of Diseases (ICD) codes and disease-specific algorithms to identify all individuals between 18-65 years of age who met criteria for de novo MS and/or focal epilepsy (Figure 1). To identify individuals with de novo epilepsy, we required a minimum of 1 year of coverage prior to an initial diagnosis of epilepsy and at least 2 total claims for epilepsy. We defined an ASM regimen change to include the addition of an ASM (that had not been previously prescribed) for at least 90 days (or 135 days for 90-day prescriptions), or the discontinuation of an ASM for at least 90 days (or 135 days for 90-day prescriptions). We compared the rates of SE and seizure-related inpatient admissions for individuals with focal epilepsy alone without MS (E-MS) versus those with MS+E, as well as the number of distinct days with claims for each of these outcomes. We compared the number of ASM treatment changes in the E-MS and MS+E groups during years 1 and 2 after the initial diagnosis of epilepsy. Analyses ≥ 3 years after the diagnosis of epilepsy were not performed due to small sample size in the MS+E group. All comparisons were Bonferroni-corrected.
Results:
Overall, there was no significant difference between the likelihood that individuals with MS+E versus E-MS would undergo seizure-related inpatient admissions or suffer from SE (Table 1). However, the subset of individuals with MS+E who had seizure-related inpatient admissions had significantly higher number of admissions and more prolonged admissions compared to those with E-MS who had seizure-related inpatient admissions. Additionally, individuals with MS+E who experienced SE had significantly more days with encounters related to SE than individuals with E-MS who experienced SE, indicating longer SE duration. Individuals with MS+E were more likely to have medication regimen changes in year 2 after the initial diagnosis of epilepsy, but not in year 1. Individuals with MS+E underwent a mean of 1.03 medication changes during year 2 compared to 0.62 for E-MS (p =0.0007) despite the fact that the median for MS+E was 0 while the median for E-MS was 1.
Conclusion:
When compared to E-MS, a subset of individuals with MS+E have more severe epilepsy as determined by higher healthcare utilization and higher number of ASM regimen changes in the second year after the initial diagnosis of epilepsy. Subsequent analyses will help us determine if specific ASM regimens are associated with superior seizure control in MS+E compared to other ASMs.
Funding:
:Supported by a grant from the American Epilepsy Society and the Epilepsy Study Consortium.