Initiation of Antiseizure Medications in Patients With Brain Abscess.

Importance: Epilepsy is a common complication of brain abscess. However, the effectiveness of antiseizure medications (ASMs) in preventing epilepsy in brain abscess survivors is unknown. Objective: To assess whether the initiation of ASMs is associated with a reduced risk of epilepsy. Design, Setting, and Participants: This retrospective cohort study conducted a target trial emulation using US commercial insurance claims data from October 1, 2016, to June 30, 2022, and followed up patients for 180 days. The study population was restricted to those with a diagnosis of brain abscess using International Statistical Classification of Diseases, Tenth Revision, Clinical Modification (ICD-10-CM) codes associated with an acute care visit. Only patients aged 18 years or older at the time of the brain abscess with at least 1 year of prior enrollment were included. Statistical analysis was performed from May to December 2024. Exposure: A priori selected study ASMs were levetiracetam, valproate, and phenytoin. A clone-censor-weight approach was used to compare the initiation of ASMs within a 45-day grace period (treatment arm) with no initiation of ASMs (control arm). Inverse probability weights were used to control for treatment selection. Main Outcomes and Measures: Study outcome was a diagnosis of epilepsy or seizure (with ICD-10-CM code) occurring 15 days or more after the index date. Weighted Kaplan-Meier models were fitted to estimate risk differences (RDs) at 90, 135, and 180 days accompanied by nonparametric bootstrapped 95% CIs. Sensitivity analyses were conducted to assess internal threats to validity. Results: Among the 572 patients included, the mean (SD) age was 61.5 (16.6) years and 353 (61.7%) were male. Of those in the treatment arm, 83 (88.3%) initiated ASMs within the first 30 days. Overall, 129 patients (22.5%) developed epilepsy during follow-up. There was no statistically significant risk difference in the probability of epilepsy incidence at each follow-up time point (RD at 90 days, -0.02% [95% CI, -4.9% to 4.8%]; RD at 135 days, 1.9% [95% CI, -5.0% to 8.5%]; RD at 180 days, 3.5% [95% CI, -4.4% to 10.8%]). Sensitivity analyses agreed with the primary findings. Conclusions and Relevance: In this cohort study of brain abscess survivors, initiation of ASMs was not associated with a reduced risk of epilepsy. Future studies should replicate the findings and consider alternative treatment protocols.